address clang-tidy warning in alib2gui

alib2gui/src/Graphics/Connection/Connection.cpp

@@ -106,7 +106,7 @@ void Connection::destroy() {
     ModelBox::disconnect(originModel, targetModel, targetConnectionBox->getSlot());
     auto removed = this->originConnectionBox->connections.erase(this);
-    Q_ASSERT(removed > 0);
+    Q_ASSERT(removed > 0); (void) removed;
     Q_ASSERT(this->targetConnectionBox->connection == this);
     this->targetConnectionBox->connection = nullptr;