net/SocketDescriptor: add AcceptNonBlock() overload without address

src/net/UniqueSocketDescriptor.hxx

@@ -76,6 +76,13 @@ public:
 		return fd == other.fd;
 	}
 
+	/**
+	 * @return an "undefined" instance on error
+	 */
+	UniqueSocketDescriptor AcceptNonBlock() const {
+		return UniqueSocketDescriptor(SocketDescriptor::AcceptNonBlock());
+	}
+
 	/**
 	 * @return an "undefined" instance on error
 	 */