Update OptionGroup::SetValue to take StringRef.

Then deal with all the fallout.

Differential Revision: https://reviews.llvm.org/D24847

llvm-svn: 282265
diff --git a/lldb/source/API/SBLanguageRuntime.cpp b/lldb/source/API/SBLanguageRuntime.cpp
index c6a96dc..d3b7514 100644
--- a/lldb/source/API/SBLanguageRuntime.cpp
+++ b/lldb/source/API/SBLanguageRuntime.cpp
@@ -15,7 +15,8 @@
 
 lldb::LanguageType
 SBLanguageRuntime::GetLanguageTypeFromString(const char *string) {
-  return Language::GetLanguageTypeFromString(string);
+  return Language::GetLanguageTypeFromString(
+      llvm::StringRef::withNullAsEmpty(string));
 }
 
 const char *