lame-but-effective workaround for self-editing UI bug, until the right fix is ready.

indra/llrender/llrender.cpp

@@ -895,7 +895,9 @@ LLVector3 LLRender::getUITranslation()
 {
 	if (mUIOffset.empty())
 	{
-		llerrs << "UI offset stack empty." << llendl;
+		//llassert(!mUIOffset.empty());
+		llwarns << "UI offset stack empty." << llendl;
+		return LLVector3(0,0,0);
 	}
 	return mUIOffset.back();
 }
@@ -904,7 +906,9 @@ LLVector3 LLRender::getUIScale()
 {
 	if (mUIScale.empty())
 	{
-		llerrs << "UI scale stack empty." << llendl;
+		//llassert(!mUIScale.empty());
+		llwarns << "UI scale stack empty." << llendl;
+		return LLVector3(1,1,1);
 	}
 	return mUIScale.back();
 }