Invalid File #5

I get the following stacktrace in my IDE Fatal Errors:
Invalid file: file:///home/ligi/git/foo/target/generated-sources/r/com/viewpagerindicator/R.java
java.lang.Throwable
at com.intellij.openapi.diagnostic.Logger.error(Logger.java:54)
at com.intellij.psi.impl.file.impl.FileManagerImpl.findFile(FileManagerImpl.java:315)
at com.intellij.psi.impl.PsiManagerImpl.findFile(PsiManagerImpl.java:182)
at com.squareup.ideaplugin.otto.OttoProjectHandler.maybeRecomputeEventClasses(OttoProjectHandler.java:167)
at com.squareup.ideaplugin.otto.OttoProjectHandler.isEventClass(OttoProjectHandler.java:74)
at com.squareup.ideaplugin.otto.OttoLineMarkerProvider.getLineMarkerInfo(OttoLineMarkerProvider.java:196)
at com.intellij.codeInsight.daemon.impl.LineMarkersPass.addLineMarkers(LineMarkersPass.java:179)
at com.intellij.codeInsight.daemon.impl.LineMarkersPass.collectInformationWithProgress(LineMarkersPass.java:118)
at com.intellij.codeInsight.daemon.impl.ProgressableTextEditorHighlightingPass.doCollectInformation(ProgressableTextEditorHighlightingPass.java:58)
at com.intellij.codeHighlighting.TextEditorHighlightingPass.collectInformation(TextEditorHighlightingPass.java:62)
at com.intellij.codeInsight.daemon.impl.PassExecutorService$ScheduledPass$1$1.run(PassExecutorService.java:357)
at com.intellij.openapi.application.impl.ApplicationImpl.tryRunReadAction(ApplicationImpl.java:1182)
at com.intellij.codeInsight.daemon.impl.PassExecutorService$ScheduledPass$1.run(PassExecutorService.java:348)
at com.intellij.openapi.progress.impl.ProgressManagerImpl.executeProcessUnderProgress(ProgressManagerImpl.java:226)
at com.intellij.codeInsight.daemon.impl.PassExecutorService$ScheduledPass.doRun(PassExecutorService.java:345)
at com.intellij.codeInsight.daemon.impl.PassExecutorService$ScheduledPass.run(PassExecutorService.java:321)
at com.intellij.concurrency.JobLauncherImpl$3.call(JobLauncherImpl.java:145)
at com.intellij.concurrency.JobLauncherImpl$3.call(JobLauncherImpl.java:142)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at com.intellij.concurrency.PrioritizedFutureTask.access$101(PrioritizedFutureTask.java:31)
at com.intellij.concurrency.PrioritizedFutureTask$1.run(PrioritizedFutureTask.java:70)
at com.intellij.concurrency.PrioritizedFutureTask.run(PrioritizedFutureTask.java:113)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:724)

This happens with IDEA Community 12.1.6