Is the given 'messages' iterator pointing at a valid message.
When this function returns TRUE, notmuch_messages_get will return a
valid object. Whereas when this function returns FALSE,
notmuch_messages_get will return NULL.
See the documentation of notmuch_query_search_messages for example
code showing how to iterate over a notmuch_messages_t object.
Is the given 'messages' iterator pointing at a valid message.
When this function returns TRUE, notmuch_messages_get will return a valid object. Whereas when this function returns FALSE, notmuch_messages_get will return NULL.
See the documentation of notmuch_query_search_messages for example code showing how to iterate over a notmuch_messages_t object.