Fixed the 'wait_until' feature.

When 'wait_until' is set to None, the program no longer crashes.

src/bandwidth_tester.py

@@ -51,10 +51,10 @@ class ClientConnectionProtocol(basic_protocols.Protocol):
 			#
 		#
 		if self.state is self.states.SEND_GROUP_ID:
-			if block:
+			if block and self.wait_until is not None:
 				time.sleep(self.wait_until-time.time())
 			#
-			if time.time() >= self.wait_until and self.sub_protocol.run(block=block):
+			if (self.wait_until is None or time.time() >= self.wait_until) and self.sub_protocol.run(block=block):
 				self.sub_protocol = basic_protocols.PushDataProtocol(self.socket, self.total_bytes,
 				                                                     data_generator=self.data_generator,
 				                                                     send_max_bytes=1024*512)