patch 8.0.0344: unlet command leaks memory

Problem:    Unlet command leaks memory. (Nikolai Pavlov)
Solution:   Free the memory on error. (closes #1497)
diff --git a/src/version.c b/src/version.c
index 5db4b11..7214854 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    344,
+/**/
     343,
 /**/
     342,