NullPointerException in getFileTypeByFile in 977

In build 977 I think I'm getting the exception reported in http://www.intellij.net/tracker/idea/viewSCR?publicId=19149, but that bug was marked fixed in 961, and when I try to report it with auto-reporting, IDEA says it's a duplicate. Does anyone know of a way to get around this? It just started happening, I've been using 977 since it came out and it worked fine.

java.lang.NullPointerException
at com.intellij.openapi.fileTypes.a.a.getFileTypeByFile(a.java:23)
at com.intellij.psi.impl.z.b(z.java:62)
at com.intellij.psi.impl.z.a(z.java:351)
at com.intellij.psi.impl.a.a.b.b(b.java:259)
at com.intellij.psi.impl.bf.findClasses(bf.java:5)
at com.intellij.codeInsight.m.a.b.f.b(f.java:74)
at com.intellij.codeInsight.m.a.b.l.visitClass(l.java:384)
at com.intellij.psi.impl.source.s.accept(s.java:135)
at com.intellij.codeInsight.m.a.b.l.a(l.java:358)
at com.intellij.codeInsight.m.a.k.a(k.java:151)
at com.intellij.codeInsight.m.a.k.a(k.java:135)
at com.intellij.codeInsight.m.a.bj$1.run(bj$1.java:8)
at com.intellij.openapi.application.b.b.runReadAction(b.java:314)
at com.intellij.codeInsight.m.a.bj.a(bj.java:41)
at com.intellij.codeInsight.m.a.bj.access$100(bj.java:7)
at com.intellij.codeInsight.m.a.bj$0.run(bj$0.java:3)
at com.intellij.progress.ProgressManager.runProcess(ProgressManager.java:27)
at com.intellij.codeInsight.m.a.bj.run(bj.java:42)