Stage 1 of clang compiler warning patches.

UI/Common/UIxToolbar.m

@@ -167,7 +167,7 @@
     [self errorWithFormat:
             @"not toolbar configuration found on SoObject: %@ (%@)",
             [self clientObject], [[self clientObject] soClass]];
-    toolbarConfig = [[NSNull null] retain];
+    toolbarConfig = (NSArray *)[[NSNull null] retain];
     return nil;
   }