patch 8.1.1664: GUI resize may cause changing Rows at a bad time

Problem:    GUI resize may cause changing Rows at a bad time. (Dominique
            Pelle)
Solution:   Postpone resizing while updating the screen.
diff --git a/src/term.c b/src/term.c
index afa622e..f1ccfcb 100644
--- a/src/term.c
+++ b/src/term.c
@@ -3425,11 +3425,15 @@
 
     if (State == HITRETURN || State == SETWSIZE)
     {
-	/* postpone the resizing */
+	// postpone the resizing
 	State = SETWSIZE;
 	return;
     }
 
+    if (updating_screen)
+	// resizing while in update_screen() may cause a crash
+	return;
+
     /* curwin->w_buffer can be NULL when we are closing a window and the
      * buffer has already been closed and removing a scrollbar causes a resize
      * event. Don't resize then, it will happen after entering another buffer.