Fix some shutdown issues in connection tracker code.

src/ssb.c

@@ -2565,6 +2565,11 @@ void tf_ssb_destroy(tf_ssb_t* ssb)
 	}
 }
 
+bool tf_ssb_is_shutting_down(tf_ssb_t* ssb)
+{
+	return ssb->shutting_down;
+}
+
 void tf_ssb_run(tf_ssb_t* ssb)
 {
 	uv_run(ssb->loop, UV_RUN_DEFAULT);

src/ssb.connections.c

@@ -86,6 +86,10 @@ typedef struct _tf_ssb_connections_get_next_t
 static void _tf_ssb_connections_get_next_work(tf_ssb_t* ssb, void* user_data)
 {
 	tf_ssb_connections_get_next_t* next = user_data;
+	if (tf_ssb_is_shutting_down(ssb))
+	{
+		return;
+	}
 	next->ready = _tf_ssb_connections_get_next_connection(next->connections, next->host, sizeof(next->host), &next->port, next->key, sizeof(next->key));
 }
 
@@ -159,6 +163,10 @@ typedef struct _tf_ssb_connections_update_t
 static void _tf_ssb_connections_update_work(tf_ssb_t* ssb, void* user_data)
 {
 	tf_ssb_connections_update_t* update = user_data;
+	if (tf_ssb_is_shutting_down(ssb))
+	{
+		return;
+	}
 	sqlite3_stmt* statement;
 	sqlite3* db = tf_ssb_acquire_db_writer(ssb);
 	if (update->attempted)

src/ssb.h

@@ -144,6 +144,13 @@ tf_ssb_t* tf_ssb_create(uv_loop_t* loop, JSContext* context, const char* db_path
 */
 void tf_ssb_destroy(tf_ssb_t* ssb);
 
+/**
+** Checking if the SSB instance is in the process of shutting down.
+** @param ssb The SSB instance.
+** @return true If the SSB instance is shutting down.
+*/
+bool tf_ssb_is_shutting_down(tf_ssb_t* ssb);
+
 /**
 ** Start optional periodic work.
 ** @param ssb The SSB instance.