patch 8.1.1640: the CursorHold autocommand takes down a balloon

Problem:    The CursorHold autocommand takes down a balloon. (Paul Jolly)
Solution:   Ignore the CursorHold pseudo-key.
diff --git a/src/getchar.c b/src/getchar.c
index f6734a7..e0c8fda 100644
--- a/src/getchar.c
+++ b/src/getchar.c
@@ -1794,7 +1794,7 @@
     may_garbage_collect = FALSE;
 #endif
 #ifdef FEAT_BEVAL_TERM
-    if (c != K_MOUSEMOVE && c != K_IGNORE)
+    if (c != K_MOUSEMOVE && c != K_IGNORE && c != K_CURSORHOLD)
     {
 	/* Don't trigger 'balloonexpr' unless only the mouse was moved. */
 	bevalexpr_due_set = FALSE;