window: Ignore input_set_pointer_image() if we don't have a pointer

https://bugs.freedesktop.org/show_bug.cgi?id=55782
diff --git a/clients/window.c b/clients/window.c
index 380962c..7b5e351 100644
--- a/clients/window.c
+++ b/clients/window.c
@@ -2691,6 +2691,9 @@
 {
 	int force = 0;
 
+	if (!input->pointer)
+		return;
+
 	if (input->pointer_enter_serial > input->cursor_serial)
 		force = 1;