patch 9.1.0579: Ex command is still executed after giving E1247

Problem:  Ex command is still executed after giving E1247.
Solution: Indicate the error properly and set cmd to NULL.
          (zeertzjq)

closes: #15241

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index c87d378..ac04272 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    579,
+/**/
     578,
 /**/
     577,