mv regsiterComparators to where it is needed

Tests/Unit/GUI/TestComboProperty.cpp

 #include "GUI/Support/Data/ComboProperty.h"
-
 #include "Tests/GTestWrapper/google_test.h"
 #include "Tests/Unit/GUI/Comparators.h"
 #include "Tests/Unit/GUI/Utils.h"
 
-class TestComboProperty : public ::testing::Test {};
+class TestComboProperty : public ::testing::Test {
+public:
+    TestComboProperty() { Comparators::registerComparators(); }
+};
 
 TEST_F(TestComboProperty, initialState)
 {

Tests/Unit/GUI/TestGUI.cpp

@@ -2,7 +2,6 @@
 // (for non-GUI unit tests, the corresponding source is Tests/GTestWrapper/TestAll.cpp).
 
 #include "Tests/GTestWrapper/google_test.h"
-#include "Tests/Unit/GUI/Comparators.h"
 #include <QCoreApplication>
 
 int main(int argc, char** argv)
@@ -10,10 +9,7 @@ int main(int argc, char** argv)
     QCoreApplication app(argc, argv);
     Q_UNUSED(app);
 
-    Comparators::registerComparators();
-
     ::testing::InitGoogleTest(&argc, argv);
 
-    // run all google tests
     return RUN_ALL_TESTS();
 }