[objc-gnustep] Fix a copy-and-paste error.

We were emitting the null class symbol in the wrong section, which meant
that programs that contained no Objective-C classes would fail to link.

llvm-svn: 350092

clang/lib/CodeGen/CGObjCGNU.cpp

@@ -1547,7 +1547,7 @@ class CGObjCGNUstep2 : public CGObjCGNUstep {
             sectionName<CategorySection>());
       if (!EmittedClass) {
         createNullGlobal(".objc_null_cls_init_ref", NULLPtr,
-            sectionName<ClassReferenceSection>());
+            sectionName<ClassSection>());
         createNullGlobal(".objc_null_class_ref", { NULLPtr, NULLPtr },
             sectionName<ClassReferenceSection>());
       }