Fix use of uninitialized value exposed by r267802. Accessors of an invalid
PresumedLoc should not be called.

llvm-svn: 267914
diff --git a/clang/lib/Frontend/TextDiagnostic.cpp b/clang/lib/Frontend/TextDiagnostic.cpp
index fdaf44d7..977af07 100644
--- a/clang/lib/Frontend/TextDiagnostic.cpp
+++ b/clang/lib/Frontend/TextDiagnostic.cpp
@@ -883,7 +883,7 @@
 void TextDiagnostic::emitIncludeLocation(SourceLocation Loc,
                                          PresumedLoc PLoc,
                                          const SourceManager &SM) {
-  if (DiagOpts->ShowLocation && PLoc.getFilename())
+  if (DiagOpts->ShowLocation && PLoc.isValid())
     OS << "In file included from " << PLoc.getFilename() << ':'
        << PLoc.getLine() << ":\n";
   else
@@ -893,7 +893,7 @@
 void TextDiagnostic::emitImportLocation(SourceLocation Loc, PresumedLoc PLoc,
                                         StringRef ModuleName,
                                         const SourceManager &SM) {
-  if (DiagOpts->ShowLocation && PLoc.getFilename())
+  if (DiagOpts->ShowLocation && PLoc.isValid())
     OS << "In module '" << ModuleName << "' imported from "
        << PLoc.getFilename() << ':' << PLoc.getLine() << ":\n";
   else
@@ -904,7 +904,7 @@
                                                 PresumedLoc PLoc,
                                                 StringRef ModuleName,
                                                 const SourceManager &SM) {
-  if (DiagOpts->ShowLocation && PLoc.getFilename())
+  if (DiagOpts->ShowLocation && PLoc.isValid())
     OS << "While building module '" << ModuleName << "' imported from "
       << PLoc.getFilename() << ':' << PLoc.getLine() << ":\n";
   else