patch 8.2.2963: GUI: mouse move may start Visual mode with a popup visible

Problem:    GUI: mouse move may start Visual mode with a popup visible.
Solution:   Add special code for mouse move. (closes #8318)
diff --git a/src/gui.c b/src/gui.c
index 2539a4f..b5ec007 100644
--- a/src/gui.c
+++ b/src/gui.c
@@ -3071,6 +3071,9 @@
      */
     switch (button)
     {
+	case MOUSE_MOVE:
+	    button_char = KE_MOUSEMOVE_XY;
+	    goto button_set;
 	case MOUSE_X1:
 	    button_char = KE_X1MOUSE;
 	    goto button_set;
@@ -4925,7 +4928,7 @@
     if (popup_visible)
 	// Generate a mouse-moved event, so that the popup can perhaps be
 	// closed, just like in the terminal.
-	gui_send_mouse_event(MOUSE_DRAG, x, y, FALSE, 0);
+	gui_send_mouse_event(MOUSE_MOVE, x, y, FALSE, 0);
 #endif
 }