Replace double negation of !FileID.isInvalid() with FileID.isValid().
+couple more of double-negated !SourceLocation.isInvalid() unfixed in r249228.

llvm-svn: 249235
diff --git a/clang/lib/Frontend/TextDiagnostic.cpp b/clang/lib/Frontend/TextDiagnostic.cpp
index d2dd192..d4e156d 100644
--- a/clang/lib/Frontend/TextDiagnostic.cpp
+++ b/clang/lib/Frontend/TextDiagnostic.cpp
@@ -777,7 +777,7 @@
   if (PLoc.isInvalid()) {
     // At least print the file name if available:
     FileID FID = SM.getFileID(Loc);
-    if (!FID.isInvalid()) {
+    if (FID.isValid()) {
       const FileEntry* FE = SM.getFileEntryForID(FID);
       if (FE && FE->isValid()) {
         OS << FE->getName();