[Gui] remove unnecessary Boolean comparisons

src/Gui/Application.cpp

@@ -546,7 +546,7 @@ void Application::open(const char* FileName, const char* Module)
     // in case of an automatically created empty document at startup
     App::Document* act = App::GetApplication().getActiveDocument();
     Gui::Document* gui = this->getDocument(act);
-    if (act && act->countObjects() == 0 && gui && gui->isModified() == false){
+    if (act && act->countObjects() == 0 && gui && !gui->isModified()){
         Command::doCommand(Command::App, "App.closeDocument('%s')", act->getName());
         qApp->processEvents(); // an update is needed otherwise the new view isn't shown
     }
@@ -2410,7 +2410,7 @@ void Application::setStyleSheet(const QString& qssFile, bool tiledBackground)
     // appear incorrect due to an outdated cache.
     // See https://doc.qt.io/qt-5/qstyle.html#unpolish-1
     // See https://forum.freecadweb.org/viewtopic.php?f=17&t=50783
-    if (d->startingUp == false) {
+    if (!d->startingUp) {
         if (mdi->style())
             mdi->style()->unpolish(qApp);
     }