patch 8.1.0641: no check for out-of-memory when converting regexp

Problem:    No check for out-of-memory when converting regexp.
Solution:   Bail out when lalloc() returns NULL. (John Marriott)
diff --git a/src/version.c b/src/version.c
index 10ba489..3150da9 100644
--- a/src/version.c
+++ b/src/version.c
@@ -800,6 +800,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    641,
+/**/
     640,
 /**/
     639,