Revert premature assumption that adding support for selected filters in Open...

Revert premature assumption that adding support for selected filters in Open Save would not affect all other file dialog operations. As is, unit tests requires all or nothing.

src/qgcunittest/UnitTest.cc

@@ -355,5 +355,9 @@ QString UnitTest::_getSaveFileName(QWidget* parent,
     Q_UNUSED(options);
     Q_UNUSED(defaultSuffix);
 
+    // Support for selectedFilter (elsewhere) is not yet implemented. Until it is added for all
+    // file dialogs, this stays here.
+    Q_ASSERT(selectedFilter == NULL);
+
     return _fileDialogResponseSingle(getSaveFileName);
 }