Fix PR1897, patch by Wilhansen Li


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@45593 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/Driver/clang.cpp b/Driver/clang.cpp
index 6e1683c..cdcbb34 100644
--- a/Driver/clang.cpp
+++ b/Driver/clang.cpp
@@ -191,6 +191,7 @@
 
   if (DotPos == std::string::npos) {
     BaseLang = langkind_c;  // Default to C if no extension.
+    return langkind_c;
   }
   
   std::string Ext = std::string(Filename.begin()+DotPos+1, Filename.end());