Fix the mutex logic in fifo.c from the espeak_ng_STATUS changes.

src/libespeak-ng/fifo.c

 	if ((status = pthread_mutex_lock(&my_mutex)) != ENS_OK)
 		return status;
 
-	if ((status = push(the_command)) != ENS_OK)
+	if ((status = push(the_command)) != ENS_OK) {
+		pthread_mutex_unlock(&my_mutex);
 		return status;
+	}
 
 	if ((status = pthread_mutex_unlock(&my_mutex)) != ENS_OK)
 		return status;
 	if (node_counter+1 >= MAX_NODE_COUNTER)
 		return ENS_FIFO_BUFFER_FULL;
 
-	if ((status = push(command1)) != ENS_OK)
+	if ((status = push(command1)) != ENS_OK) {
+		pthread_mutex_unlock(&my_mutex);
 		return status;
+	}
 
-	if ((status = push(command2)) != ENS_OK)
+	if ((status = push(command2)) != ENS_OK) {
+		pthread_mutex_unlock(&my_mutex);
 		return status;
+	}
 
 	if ((status = pthread_mutex_unlock(&my_mutex)) != ENS_OK)
 		return status;