patch 8.2.0827: Vim9: crash in :defcompile

Problem:    Vim9: crash in :defcompile.
Solution:   Fix off-by-one error.
diff --git a/src/userfunc.c b/src/userfunc.c
index 4a12c19..469dcc1 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -3348,6 +3348,7 @@
 		    hi = func_hashtab.ht_array;
 		    ht_used = func_hashtab.ht_used;
 		    todo = (int)ht_used;
+		    --hi;
 		}
 	    }
 	}