patch 8.2.4687: "vimgrep /\%v/ *" may cause a crash

Problem:    "vimgrep /\%v/ *" may cause a crash.
Solution:   When compiling the pattern with the old engine fails, restore the
            regprog of the new engine instead of leaving it NULL.
            (closes #10079)
diff --git a/src/version.c b/src/version.c
index fffd85f..23dede0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4687,
+/**/
     4686,
 /**/
     4685,