[libclang] Fix error handler in translateSourceLocation.

[simon_tatham]

Summary

Given an invalid SourceLocation, translateSourceLocation will call
clang_getNullLocation, and then do nothing with the result. But
clang_getNullLocation has no side effects: it just constructs and
returns a null CXSourceLocation value.

Surely the intention was to return that null CXSourceLocation to
the caller, instead of throwing it away and pressing on anyway.

[miyuki]

This change is pretty obvious. LGTM.

clang/tools/libclang/CXSourceLocation.h

 
 namespace cxloc {
 
 /// Translate a Clang source location into a CIndex source location.
 static inline CXSourceLocation 
 translateSourceLocation(const SourceManager &SM, const LangOptions &LangOpts,
                         SourceLocation Loc) {
   if (Loc.isInvalid())
-    clang_getNullLocation();
+    return clang_getNullLocation();
 
   CXSourceLocation Result = { { &SM, &LangOpts, },
                               Loc.getRawEncoding() };
   return Result;
 }
   
 /// Translate a Clang source location into a CIndex source location.
 static inline CXSourceLocation translateSourceLocation(ASTContext &Context,