patch 9.1.0254: [security]: Heap buffer overflow when calling complete_add() in 'cfu'

Problem:  [security]: Heap buffer overflow when calling complete_add()
          in the first call of 'completefunc'
Solution: Call check_cursor() after calling 'completefunc' (zeertzjq)

closes: #14391

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/insexpand.c b/src/insexpand.c
index 9b5e5de..93a56a8 100644
--- a/src/insexpand.c
+++ b/src/insexpand.c
@@ -2741,6 +2741,7 @@
     --textlock;
 
     curwin->w_cursor = pos;	// restore the cursor position
+    check_cursor();  // make sure cursor position is valid, just in case
     validate_cursor();
     if (!EQUAL_POS(curwin->w_cursor, pos))
     {
@@ -4606,6 +4607,7 @@
 
     State = save_State;
     curwin->w_cursor = pos;	// restore the cursor position
+    check_cursor();  // make sure cursor position is valid, just in case
     validate_cursor();
     if (!EQUAL_POS(curwin->w_cursor, pos))
     {