FS-9714: [mod_conference] fix crash due to race on closing file handles when…

FS-9714: [mod_conference] fix crash due to race on closing file handles when playing a file to a conference via api command as a conference is shutting down

src/mod/applications/mod_conference/mod_conference.c

@@ -776,6 +776,8 @@ void *SWITCH_THREAD_FUNC conference_thread_run(switch_thread_t *thread, void *ob
 		}
 	}
 
+	switch_mutex_lock(conference->mutex);
+
 	/* Close Unused Handles */
 	if (conference->fnode) {
 		conference_file_node_t *fnode, *cur;
@@ -804,6 +806,8 @@ void *SWITCH_THREAD_FUNC conference_thread_run(switch_thread_t *thread, void *ob
 		switch_core_destroy_memory_pool(&pool);
 	}
 
+	switch_mutex_unlock(conference->mutex);
+
 	/* Wait till everybody is out */
 	conference_utils_clear_flag_locked(conference, CFLAG_RUNNING);
 	switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_DEBUG, "Write Lock ON\n");