Fix <rdar://problem/6450964> clang on xcode: Assertion failed: (RecordForDecl && "lookupFieldDeclForIvar no storage for class").

This was a recent regression caused by r61043 (related to code gen. for ivar references).

Fariborz, please review. I have some other concerns related to code generation for ivars that we can discuss later.

llvm-svn: 61134
diff --git a/clang/lib/AST/DeclObjC.cpp b/clang/lib/AST/DeclObjC.cpp
index 9e803b7..12c2245 100644
--- a/clang/lib/AST/DeclObjC.cpp
+++ b/clang/lib/AST/DeclObjC.cpp
@@ -369,6 +369,8 @@
 ///
 FieldDecl *ObjCInterfaceDecl::lookupFieldDeclForIvar(ASTContext &Context, 
                                                      const ObjCIvarDecl *ivar) {
+  if (!RecordForDecl)
+    addRecordToClass(Context);
   assert(RecordForDecl && "lookupFieldDeclForIvar no storage for class");
   DeclarationName Member = ivar->getDeclName();
   DeclContext::lookup_result Lookup = RecordForDecl->lookup(Context, Member);