fix NPE on missing currency conversion

[teosarca]

Avoid NPE in case of missing currency conversion. Instead throw a much more understandable exception.

The triggering exception was:

de.metas.acct.doc.PostingException: NullPointerException
 Buchungsstatus: Verbuchungs-Fehler (Error)
 Belegnummer: MMatchPO[1004524,Qty=26.00000,C_OrderLine_ID=1042334,M_InOutLine_ID=1030499,C_InvoiceLine_ID=0]
 Preserve Posted status: false
Additional parameters:
 issueCategory: ACCOUNTING
 recordRef: TableRecordReference{tableName=M_MatchPO, recordId=1004524}
	at org.compiere.acct.Doc.newPostingException(Doc.java:1844)
	at org.compiere.acct.Doc$1.doCatch(Doc.java:376)
	at org.adempiere.ad.trx.api.impl.TrxCallableWrappers$3.doCatch(TrxCallableWrappers.java:160)
	at org.adempiere.ad.trx.api.impl.AbstractTrxManager.call0(AbstractTrxManager.java:786)
	at org.adempiere.ad.trx.api.impl.AbstractTrxManager.call(AbstractTrxManager.java:666)
	at org.adempiere.ad.trx.api.impl.AbstractTrxManager.call(AbstractTrxManager.java:567)
	at org.adempiere.ad.trx.api.impl.AbstractTrxManager.call(AbstractTrxManager.java:498)
	at org.adempiere.ad.trx.api.impl.AbstractTrxManager.run(AbstractTrxManager.java:484)
	at org.adempiere.ad.trx.api.ITrxManager.runInThreadInheritedTrx(ITrxManager.java:218)
	at de.metas.acct.doc.AcctDocRequiredServicesFacade.runInThreadInheritedTrx(AcctDocRequiredServicesFacade.java:147)
	at org.compiere.acct.Doc.post(Doc.java:363)
	at de.metas.acct.api.impl.PostingRequestBuilder.postIt_Directly(PostingRequestBuilder.java:178)
	at de.metas.acct.api.impl.PostingRequestBuilder.invokeRunnable(PostingRequestBuilder.java:398)
	at de.metas.acct.api.impl.PostingRequestBuilder.lambda$postAfterTrxCommit$0(PostingRequestBuilder.java:391)
	at org.adempiere.ad.trx.api.impl.AutoCommitTrxListenerManager.execute(AutoCommitTrxListenerManager.java:72)
	at org.adempiere.ad.trx.api.impl.AutoCommitTrxListenerManager.registerListener(AutoCommitTrxListenerManager.java:48)
	at org.adempiere.ad.trx.api.ITrxListenerManager$RegisterListenerRequest.registerHandlingMethod(ITrxListenerManager.java:140)
	at de.metas.acct.api.impl.PostingRequestBuilder.postAfterTrxCommit(PostingRequestBuilder.java:391)
	at de.metas.acct.api.impl.PostingRequestBuilder.postIt(PostingRequestBuilder.java:127)
	at de.metas.acct.posting.server.AccountingService.handleRequest(AccountingService.java:64)
	at de.metas.acct.posting.DocumentPostingBusService$DocumentPostRequestHandlerAsEventListener.handleRequest(DocumentPostingBusService.java:154)
	at de.metas.acct.posting.DocumentPostingBusService$DocumentPostRequestHandlerAsEventListener.lambda$onEvent$0(DocumentPostingBusService.java:147)
	at de.metas.event.log.EventLogUserService.invokeHandlerAndLog(EventLogUserService.java:164)
	at de.metas.acct.posting.DocumentPostingBusService$DocumentPostRequestHandlerAsEventListener.onEvent(DocumentPostingBusService.java:145)
	at de.metas.event.impl.EventBus.invokeEventListenerWithLogging(EventBus.java:329)
	at de.metas.event.impl.EventBus.invokeEventListener(EventBus.java:315)
	at de.metas.event.impl.EventBus.access$200(EventBus.java:58)
	at de.metas.event.impl.EventBus$GuavaEventListenerAdapter.onEvent(EventBus.java:304)
	at sun.reflect.GeneratedMethodAccessor142.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at reflect.Method.invoke(Method.java:498)
	at com.google.common.eventbus.Subscriber.invokeSubscriberMethod(Subscriber.java:91)
	at com.google.common.eventbus.Subscriber$SynchronizedSubscriber.invokeSubscriberMethod(Subscriber.java:150)
	at com.google.common.eventbus.Subscriber$1.run(Subscriber.java:76)
	at com.google.common.util.concurrent.MoreExecutors$DirectExecutor.execute(MoreExecutors.java:399)
	at com.google.common.eventbus.Subscriber.dispatchEvent(Subscriber.java:71)
	at com.google.common.eventbus.Dispatcher$PerThreadQueuedDispatcher.dispatch(Dispatcher.java:116)
	at com.google.common.eventbus.EventBus.post(EventBus.java:217)
	at de.metas.event.impl.EventBus.postEvent(EventBus.java:250)
	at de.metas.acct.posting.DocumentPostingBusService.postRequest(DocumentPostingBusService.java:75)
	at de.metas.acct.api.impl.PostingRequestBuilder.postIt_Enqueue(PostingRequestBuilder.java:148)
	at de.metas.acct.api.impl.PostingRequestBuilder.invokeRunnable(PostingRequestBuilder.java:398)
	at de.metas.acct.api.impl.PostingRequestBuilder.lambda$postAfterTrxCommit$0(PostingRequestBuilder.java:391)
	at org.adempiere.ad.trx.api.impl.AutoCommitTrxListenerManager.execute(AutoCommitTrxListenerManager.java:72)
	at org.adempiere.ad.trx.api.impl.AutoCommitTrxListenerManager.registerListener(AutoCommitTrxListenerManager.java:48)
	at org.adempiere.ad.trx.api.ITrxListenerManager$RegisterListenerRequest.registerHandlingMethod(ITrxListenerManager.java:140)
	at de.metas.acct.api.impl.PostingRequestBuilder.postAfterTrxCommit(PostingRequestBuilder.java:391)
	at de.metas.acct.api.impl.PostingRequestBuilder.postIt(PostingRequestBuilder.java:116)
	at de.metas.acct.posting.server.accouting_docs_to_repost_db_table.AccoutingDocsToRepostDBTableWatcher.enqueueForReposting(AccoutingDocsToRepostDBTableWatcher.java:125)
	at de.metas.acct.posting.server.accouting_docs_to_repost_db_table.AccoutingDocsToRepostDBTableWatcher.enqueueAllForReposting(AccoutingDocsToRepostDBTableWatcher.java:104)
	at de.metas.acct.posting.server.accouting_docs_to_repost_db_table.AccoutingDocsToRepostDBTableWatcher.run(AccoutingDocsToRepostDBTableWatcher.java:79)
	at Thread.run(Thread.java:748)
Caused by: NullPointerException
	at de.metas.costing.impl.CostingService.convertToAcctSchemaCurrency(CostingService.java:219)
	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183)
	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
	at java.util.stream.Streams$StreamBuilderImpl.forEachRemaining(Streams.java:419)
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:482)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:472)
	at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173)
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:485)
	at java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:272)
	at java.util.stream.Streams$StreamBuilderImpl.forEachRemaining(Streams.java:419)
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:482)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:472)
	at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:566)
	at de.metas.costing.impl.CostingService.createCostDetail(CostingService.java:138)
	at de.metas.acct.doc.AcctDocRequiredServicesFacade.createCostDetail(AcctDocRequiredServicesFacade.java:295)
	at org.compiere.acct.DocLine_MatchPO.createCostDetails(DocLine_MatchPO.java:141)
	at org.compiere.acct.Doc_MatchPO.createFacts(Doc_MatchPO.java:110)
	at org.compiere.acct.Doc.postLogic(Doc.java:566)
	at org.compiere.acct.Doc.post0(Doc.java:477)
	at org.compiere.acct.Doc.access$000(Doc.java:158)
	at org.compiere.acct.Doc$1.run(Doc.java:370)
	at org.adempiere.ad.trx.api.impl.TrxCallableWrappers$3.call(TrxCallableWrappers.java:147)
	at org.adempiere.ad.trx.api.impl.TrxCallableWrappers$3.call(TrxCallableWrappers.java:137)
	at org.adempiere.ad.trx.api.impl.AbstractTrxManager.call0(AbstractTrxManager.java:753)
	... 48 more