Fix broker refusing to start if only websockets listeners were defined.

Closes #1740. Thanks to OkenKhuman.

ChangeLog.txt

@@ -1,5 +1,7 @@
 Broker:
 - Fix usage message only mentioning v3.1.1. Closes #1713.
+- Fix broker refusing to start if only websockets listeners were defined.
+  Closes #1740.
 
 Client library:
 - Improved documentation around connect callback return codes. Close #1730.

src/mosquitto.c

@@ -333,10 +333,6 @@ int main(int argc, char *argv[])
 #endif
 		}
 	}
-	if(listensock == NULL){
-		log__printf(NULL, MOSQ_LOG_ERR, "Error: Unable to start any listening sockets, exiting.");
-		return 1;
-	}
 
 	rc = drop_privileges(&config, false);
 	if(rc != MOSQ_ERR_SUCCESS) return rc;