patch 7.4.1827
Problem:    No error when invoking a callback when it's not safe.
Solution:   Add an error message.  Avoid the error when freeing a channel.
diff --git a/src/version.c b/src/version.c
index 373aff2..266e591 100644
--- a/src/version.c
+++ b/src/version.c
@@ -754,6 +754,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1827,
+/**/
     1826,
 /**/
     1825,