notmuch_tags_advance: Make safe against excessive calls.

Previously, an excess call would have caused a crash. Now it simply
does nothing. Also, make notmuch_tags_get use a similar, consistent
early return for a NULL iterator.

1 files changed, 6 insertions, 3 deletions

diff --git a/lib/tags.c b/lib/tags.c
index afc132c5..85507e91 100644
--- a/lib/tags.c
+++ b/lib/tags.c
@@ -97,15 +97,18 @@ notmuch_tags_has_more (notmuch_tags_t *tags)
 const char *
 notmuch_tags_get (notmuch_tags_t *tags)
 {
-    if (tags->iterator)
-	return (char *) tags->iterator->data;
-    else
+    if (tags->iterator == NULL)
 	return NULL;
+
+    return (char *) tags->iterator->data;
 }
 
 void
 notmuch_tags_advance (notmuch_tags_t *tags)
 {
+    if (tags->iterator == NULL)
+	return;
+
     tags->iterator = tags->iterator->next;
 }