patch 7.4.717
Problem:    ":let list += list" can change a locked list.
Solution:   Check for the lock earlier. (Olaf Dabrunz)
diff --git a/src/version.c b/src/version.c
index abaa995..ee6d301 100644
--- a/src/version.c
+++ b/src/version.c
@@ -742,6 +742,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    717,
+/**/
     716,
 /**/
     715,