--- ..\..\a\src\iup_globalattrib.c	Tue Apr 23 14:33:33 2019
+++ iup_globalattrib.c	Sat May 25 08:42:08 2019
@@ -133,7 +133,7 @@
       iupdrvWarpPointer(x, y);
     return;
   }
-  if (iupStrEqual(name, "MOUSEBUTTON"))
+  if (value != NULL && iupStrEqual(name, "MOUSEBUTTON"))
   {
     int x, y, status;
     char bt;