Generation of pb.h/cc-files fails if proto file is in a linked folder

What steps will reproduce the problem?
1.e.g create a c++ project
2.properties/c/c++ general/path and symbols/link folder...
3.link to folder in the file system

What is the expected output? What do you see instead?
generated files -> nothing

What version of the product are you using? On what operating system?
protobuf-dt 1.3.2
same on Indigo

eclipse.buildId=I20120608-1400
java.version=1.6.0_22
java.vendor=Sun Microsystems Inc.
BootLoader constants: OS=win32, ARCH=x86, WS=win32, NL=de_DE
Framework arguments:  -product org.eclipse.epp.package.cpp.product
Command-line arguments:  -os win32 -ws win32 -arch x86 -product 
org.eclipse.epp.package.cpp.product

Please provide any additional information below.

java.lang.NullPointerException
    at com.google.eclipse.protobuf.ui.protoc.command.ImportRootsProtocOption.singleImportRoot(ImportRootsProtocOption.java:73)
    at com.google.eclipse.protobuf.ui.protoc.command.ImportRootsProtocOption.singleImportRoot(ImportRootsProtocOption.java:65)
    at com.google.eclipse.protobuf.ui.protoc.command.ImportRootsProtocOption.initialize(ImportRootsProtocOption.java:49)
    at com.google.eclipse.protobuf.ui.protoc.command.ImportRootsProtocOption.addOptionToCommand(ImportRootsProtocOption.java:39)
    at com.google.eclipse.protobuf.ui.protoc.command.ProtocCommandBuilder.buildCommand(ProtocCommandBuilder.java:50)
    at com.google.eclipse.protobuf.ui.builder.protoc.ProtobufBuildParticipant.build(ProtobufBuildParticipant.java:61)
    at org.eclipse.xtext.builder.impl.RegistryBuilderParticipant.build(RegistryBuilderParticipant.java:60)
    at org.eclipse.xtext.builder.impl.XtextBuilder.doBuild(XtextBuilder.java:161)
    at org.eclipse.xtext.builder.impl.XtextBuilder.fullBuild(XtextBuilder.java:188)
    at org.eclipse.xtext.builder.impl.XtextBuilder.build(XtextBuilder.java:85)
    at org.eclipse.core.internal.events.BuildManager$2.run(BuildManager.java:728)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:199)
    at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:239)
    at org.eclipse.core.internal.events.BuildManager$1.run(BuildManager.java:292)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:295)
    at org.eclipse.core.internal.events.BuildManager.basicBuildLoop(BuildManager.java:351)
    at org.eclipse.core.internal.events.BuildManager.build(BuildManager.java:374)
    at org.eclipse.core.internal.resources.Workspace.buildInternal(Workspace.java:513)
    at org.eclipse.core.internal.resources.Workspace.build(Workspace.java:432)
    at org.eclipse.ui.actions.BuildAction$1.runInWorkspace(BuildAction.java:305)
    at org.eclipse.core.internal.resources.InternalWorkspaceJob.run(InternalWorkspaceJob.java:38)
    at org.eclipse.core.internal.jobs.Worker.run(Worker.java:54)
Original issue reported on code.google.com by jochen.k...@burkert.com on 21 Aug 2012 at 4:43
Merged into: #191
rytina / protobuf-dt

Generation of pb.h/cc-files fails if proto file is in a linked folder #223
