ResourceUtils.filterStylesheets throws NPE if resource is not found (null)

[gako]

ResourceUtils.java Line 91

resource = resourceHandler.createResource
...
stylesheets.add(**resource**.getRequestPath());

In special cases a resourceHandler can return null for a resource if it is not found... In this case the resourceUtils class throws a Nullpointer exception. It would be nice if this is handled gracefully.

if (resource!=null) {
stylesheets.add(**resource**.getRequestPath());
}

StrackeTrace of Exception
java.lang.NullPointerException
at org.primefaces.util.ResourceUtils.filterStylesheets(ResourceUtils.java:96)
at org.primefaces.context.PrimePartialResponseWriter.startMetadataIfNecessary(PrimePartialResponseWriter.java:287)
at org.primefaces.context.PrimePartialResponseWriter.startUpdate(PrimePartialResponseWriter.java:142)
at org.omnifaces.context.OmniPartialViewContext$OmniPartialResponseWriter.startUpdate(OmniPartialViewContext.java:323)
at com.sun.faces.context.PartialViewContextImpl.renderState(PartialViewContextImpl.java:482)
at com.sun.faces.context.PartialViewContextImpl.processPartial(PartialViewContextImpl.java:325)
at org.primefaces.context.PrimePartialViewContext.processPartial(PrimePartialViewContext.java:57)
at javax.faces.context.PartialViewContextWrapper.processPartial(PartialViewContextWrapper.java:219)
at org.omnifaces.context.OmniPartialViewContext.processPartial(OmniPartialViewContext.java:144)
at javax.faces.component.UIViewRoot.encodeChildren(UIViewRoot.java:1004)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1856)
at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:432)
at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:134)
at com.ocpsoft.pretty.faces.application.PrettyViewHandler.renderView(PrettyViewHandler.java:163)
at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:337)
at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:337)
at org.omnifaces.viewhandler.OmniViewHandler.renderView(OmniViewHandler.java:115)
at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:337)
at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:337)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:120)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:219)

1) Environment

• PrimeFaces version: 6.0.5
• Application server + version: Paraya 4.1.1.165 (GF 4.1.1)
• Affected browsers: Serverside error

2) Expected behavior

Not available resource is gracefully ignored

3) Actual behavior

NullPointerException is thrown

4) Steps to reproduce

Open a page that required additional resources during an action. Then make sure the session is lost in the background (session timeout, server restart,...)
..

[gako]

The same is probably also true for ResourceUtils.filterScripts (line 119) but I havn't encouterd this yet.

[tandraschko]

So we should