[MNG-6626] fix DefaultExceptionHandler NPE

[seregamorph]

https://issues.apache.org/jira/browse/MNG-6626
DefaultExceptionHandler.handleException throws NPE in case if root cause is NoClassDefFoundError with null message.

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[seregamorph]

Diagnostic of failed build before the fix:

[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  6.590 s
[INFO] Finished at: 2019-04-05T23:37:49+03:00
[INFO] ------------------------------------------------------------------------
[ERROR] Error executing Maven.
[ERROR] null

Diagnostics of failure after the fix:

[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  6.274 s
[INFO] Finished at: 2019-04-05T23:39:06+03:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal com.jivesoftware:soy-buildtime-compile-plugin:2019.3.0-SNAPSHOT:soy-compile (default) on project jive-core: Execution default of goal com.jivesoftware:soy-buildtime-compile-plugin:2019.3.0-SNAPSHOT:soy-compile failed: A required class was missing while executing com.jivesoftware:soy-buildtime-compile-plugin:2019.3.0-SNAPSHOT:soy-compile: null
[ERROR] -----------------------------------------------------
[ERROR] realm =    plugin>com.jivesoftware:soy-buildtime-compile-plugin:2019.3.0-SNAPSHOT
[ERROR] strategy = org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy
[ERROR] urls[0] = file:/Users/morph/Projects/aurea/jive-cloud-application/soy-buildtime-compile-plugin/target/classes/
[ERROR] urls[1] = file:/Users/morph/.m2/repository/com/google/inject/guice/4.1.0/guice-4.1.0.jar
[ERROR] urls[2] = file:/Users/morph/.m2/repository/aopalliance/aopalliance/1.0/aopalliance-1.0.jar
[ERROR] urls[3] = file:/Users/morph/.m2/repository/com/jivesoftware/google-closure/1.0-jive2/google-closure-1.0-jive2.jar
[ERROR] urls[4] = file:/Users/morph/.m2/repository/com/google/inject/extensions/guice-multibindings/4.1.0/guice-multibindings-4.1.0.jar
[ERROR] urls[5] = file:/Users/morph/.m2/repository/com/google/guava/guava/20.0/guava-20.0.jar
[ERROR] urls[6] = file:/Users/morph/.m2/repository/org/apache/commons/commons-lang3/3.3.2/commons-lang3-3.3.2.jar
[ERROR] urls[7] = file:/Users/morph/.m2/repository/log4j/log4j/1.2.17/log4j-1.2.17.jar
[ERROR] urls[8] = file:/Users/morph/.m2/repository/com/google/inject/extensions/guice-assistedinject/4.1.0/guice-assistedinject-4.1.0.jar
[ERROR] urls[9] = file:/Users/morph/.m2/repository/org/apache/maven/shared/file-management/1.2.1/file-management-1.2.1.jar
[ERROR] urls[10] = file:/Users/morph/.m2/repository/org/apache/maven/shared/maven-shared-io/1.1/maven-shared-io-1.1.jar
[ERROR] urls[11] = file:/Users/morph/.m2/repository/org/codehaus/plexus/plexus-utils/1.5.6/plexus-utils-1.5.6.jar
[ERROR] urls[12] = file:/Users/morph/.m2/repository/junit/junit/4.12/junit-4.12.jar
[ERROR] urls[13] = file:/Users/morph/.m2/repository/commons-io/commons-io/2.4/commons-io-2.4.jar
[ERROR] urls[14] = file:/Users/morph/.m2/repository/com/google/javascript/closure-compiler-unshaded/v20160911/closure-compiler-unshaded-v20160911.jar
[ERROR] urls[15] = file:/Users/morph/.m2/repository/com/google/javascript/closure-compiler-externs/v20160911/closure-compiler-externs-v20160911.jar
[ERROR] urls[16] = file:/Users/morph/.m2/repository/args4j/args4j/2.0.26/args4j-2.0.26.jar
[ERROR] urls[17] = file:/Users/morph/.m2/repository/com/google/protobuf/protobuf-java/2.5.0/protobuf-java-2.5.0.jar
[ERROR] urls[18] = file:/Users/morph/.m2/repository/com/google/code/gson/gson/2.5/gson-2.5.jar
[ERROR] urls[19] = file:/Users/morph/.m2/repository/com/google/code/findbugs/jsr305/1.3.9/jsr305-1.3.9.jar
[ERROR] urls[20] = file:/Users/morph/.m2/repository/com/google/jsinterop/jsinterop-annotations/1.0.0/jsinterop-annotations-1.0.0.jar
[ERROR] urls[21] = file:/Users/morph/Projects/aurea/jive-cloud-application/soy-common/target/classes/
[ERROR] urls[22] = file:/Users/morph/.m2/repository/org/slf4j/slf4j-log4j12/1.7.25/slf4j-log4j12-1.7.25.jar
[ERROR] urls[23] = file:/Users/morph/.m2/repository/caja/caja/r4884/caja-r4884.jar
[ERROR] urls[24] = file:/Users/morph/.m2/repository/caja/htmlparser/r4209/htmlparser-r4209.jar
[ERROR] urls[25] = file:/Users/morph/.m2/repository/com/googlecode/json-simple/json-simple/1.1/json-simple-1.1.jar
[ERROR] urls[26] = file:/Users/morph/.m2/repository/xerces/xercesImpl/2.9.1/xercesImpl-2.9.1.jar
[ERROR] urls[27] = file:/Users/morph/.m2/repository/xml-apis/xml-apis/1.3.04/xml-apis-1.3.04.jar
[ERROR] urls[28] = file:/Users/morph/.m2/repository/org/codehaus/jettison/jettison/1.2/jettison-1.2.jar
[ERROR] urls[29] = file:/Users/morph/.m2/repository/commons-codec/commons-codec/1.7/commons-codec-1.7.jar
[ERROR] urls[30] = file:/Users/morph/.m2/repository/javax/annotation/javax.annotation-api/1.3.2/javax.annotation-api-1.3.2.jar
[ERROR] Number of foreign imports: 1
[ERROR] import: Entry[import  from realm ClassRealm[project>com.jivesoftware:jive-core:2019.3.0-SNAPSHOT, parent: ClassRealm[maven.api, parent: null]]]
[ERROR] 
[ERROR] -----------------------------------------------------
[ERROR] : NoClassDefFoundError: com/google/common/io/InputSupplier: com.google.common.io.InputSupplier
[ERROR] -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginContainerException
[ERROR] 

If enable debug logging (-X) it gives all detailed message 👍

[seregamorph]

@slachiewicz thanks for the review. Is there a chance that this change will be accepted?

[slachiewicz]

Thx @seregamorph !