VWR-24263: Crash fix for notecards with negative text length

indra/llinventory/llnotecard.cpp

@@ -199,7 +199,7 @@ bool LLNotecard::importStream(std::istream& str)
 		return FALSE;
 	}
 
-	if(text_len > mMaxText)
+	if(text_len > mMaxText || text_len < 0)
 	{
 		llwarns << "Invalid Linden text length: " << text_len << llendl;
 		return FALSE;