[VDE] Proper parent lookup syncs group-by box again (#6396)

* [VDE] Proper parent lookup syncs group-by box again

* [VDE] Proper lib inclusion.

* [VDE] Lint.

libcockatrice_utility/libcockatrice/utility/qt_utils.h

@@ -0,0 +1,20 @@
+#ifndef COCKATRICE_QT_UTILS_H
+#define COCKATRICE_QT_UTILS_H
+#include <QObject>
+
+namespace QtUtils
+{
+template <typename T> T *findParentOfType(const QObject *obj)
+{
+    const QObject *p = obj ? obj->parent() : nullptr;
+    while (p) {
+        if (auto casted = qobject_cast<T *>(const_cast<QObject *>(p))) {
+            return casted;
+        }
+        p = p->parent();
+    }
+    return nullptr;
+}
+} // namespace QtUtils
+
+#endif // COCKATRICE_QT_UTILS_H