fix: server shutdown hangs if no client address

If the client never shared their ILP address and server.close() is called or the connection is closed from the server, the Promise would never resolve/send loop would never exit

src/connection.ts

@@ -966,6 +966,7 @@ export class Connection extends EventEmitter {
     }
     if (!this._destinationAccount) {
       this.log.debug('not sending because we do not know the client\'s address')
+      this.safeEmit('_send_loop_finished')
       return
     }
 

test/connection.test.ts

@@ -133,6 +133,11 @@ describe('Connection', function () {
       assert.calledOnce(closeSpy)
     })
 
+    it('should resolve even if the remote address is unknown', async function () {
+      delete this.serverConn._destinationAccount
+      await this.serverConn.end()
+    })
+
     it('should close all outgoing streams', async function () {
       const clientSpy = {
         stream1: {