Resolves: fdo#85032 max len property of -1 -> crash

Change-Id: Ief903c619204f01784e93fd5e2d582632cef032e

vcl/source/control/edit.cxx

@@ -2468,7 +2468,7 @@ bool Edit::IsInsertMode() const
 
 void Edit::SetMaxTextLen(sal_Int32 nMaxLen)
 {
-    mnMaxTextLen = nMaxLen ? nMaxLen : EDIT_NOLIMIT;
+    mnMaxTextLen = nMaxLen > 0 ? nMaxLen : EDIT_NOLIMIT;
 
     if ( mpSubEdit )
         mpSubEdit->SetMaxTextLen( mnMaxTextLen );