add an assertion from Alexei Svitkine!



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@64503 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Lex/PPLexerChange.cpp b/lib/Lex/PPLexerChange.cpp
index 244281f..ec3447a 100644
--- a/lib/Lex/PPLexerChange.cpp
+++ b/lib/Lex/PPLexerChange.cpp
@@ -227,8 +227,8 @@
     
     // We're done with the #included file.
     CurLexer.reset();
-  }
-  else {
+  } else {
+    assert(CurPTHLexer && "Got EOF but no current lexer set!");
     CurPTHLexer->getEOF(Result);
     CurPTHLexer.reset();
   }