Fix raw lex crash and -frewrite-includes noeol-at-eof failure

Raw lexers don't have a preprocessor so we need to null check.

llvm-svn: 197245
diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp
index c071455..009f18a 100644
--- a/clang/lib/Lex/Lexer.cpp
+++ b/clang/lib/Lex/Lexer.cpp
@@ -2460,7 +2460,8 @@
     FormTokenWithChars(Result, CurPtr, tok::eod);
 
     // Restore comment saving mode, in case it was disabled for directive.
-    resetExtendedTokenMode();
+    if (PP)
+      resetExtendedTokenMode();
     return true;  // Have a token.
   }