trie filtering: ensure we don't misuse string_extend.

* filter.c (trie_filter_string): If a trie node is associated
with a filter substitute object that isn't a character or
string, then convert that to a string using tostringp.
It could be an integer. If so and we feed that to
string_extend, it will extend the string.

1 files changed, 2 insertions, 0 deletions

diff --git a/filter.c b/filter.c
index 11637a29..37a27bcb 100644
--- a/filter.c
+++ b/filter.c
@@ -280,6 +280,8 @@ static val trie_filter_string(val filter, val str)
     }
 
     if (match) {
+      if (!stringp(subst) && chrp(subst))
+        subst = tostringp(subst);
       string_extend(out, subst);
       i = plus(match, one);
     } else {