(fix) don't allow controller errors block GUI loading

Author: ronso0

src/controllers/midi/midicontroller.cpp

@@ -137,6 +137,7 @@ void MidiController::createOutputHandlers() {
 
     if (!failures.isEmpty()) {
         ErrorDialogProperties* props = ErrorDialogHandler::instance()->newDialogProperties();
+        props->setModal(false);
         props->setType(DLG_WARNING);
         props->setTitle(tr("MixxxControl(s) not found"));
         props->setText(tr(

src/controllers/scripting/legacy/controllerscriptenginelegacy.cpp

@@ -232,6 +232,7 @@ bool ControllerScriptEngineLegacy::evaluateScriptFile(const QFileInfo& scriptFil
                                                input.errorString());
         // Set up error dialog
         ErrorDialogProperties* props = ErrorDialogHandler::instance()->newDialogProperties();
+        props->setModal(false);
         props->setType(DLG_WARNING);
         props->setTitle(tr("Controller Mapping File Problem"));
         props->setText(tr("The mapping for controller \"%1\" cannot be opened.")