patch 8.2.3284: no error for insert() or remove() changing a locked blob

Problem:    No error for insert() or remove() changing a locked blob.
Solution:   Check a blob is not locked before changing it. (Sean Dewar,
            closes #8696)
diff --git a/src/blob.c b/src/blob.c
index 57fe58b..2138ac0 100644
--- a/src/blob.c
+++ b/src/blob.c
@@ -412,16 +412,19 @@
  * "remove({blob})" function
  */
     void
-blob_remove(typval_T *argvars, typval_T *rettv)
+blob_remove(typval_T *argvars, typval_T *rettv, char_u *arg_errmsg)
 {
+    blob_T	*b = argvars[0].vval.v_blob;
     int		error = FALSE;
     long	idx;
     long	end;
 
+    if (b != NULL && value_check_lock(b->bv_lock, arg_errmsg, TRUE))
+	return;
+
     idx = (long)tv_get_number_chk(&argvars[1], &error);
     if (!error)
     {
-	blob_T  *b = argvars[0].vval.v_blob;
 	int	len = blob_len(b);
 	char_u  *p;