Backing out patch for bug 328755 due to crash regression bug 328842. r=darin.

xpcom/string/src/nsTSubstring.cpp

@@ -299,7 +299,7 @@ void
 nsTSubstring_CharT::Assign( const char_type* data, size_type length )
   {
       // unfortunately, some callers pass null :-(
-    if (!data || length == 0)
+    if (!data)
       {
         Truncate();
         return;