Add QTC_GUARD

Similar to QTC_CHECK, but has the boolean result of the condition as
value. Use it in the form

if (QTC_GUARD(condition)) { ... }

Replace some occurrences of

QTC_CHECK(condition)
if (condition) { .... }

Change-Id: I8eea02f869eb7a183dfbf4810dace48097880519
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Tobias Hunger <tobias.hunger@theqtcompany.com>
Reviewed-by: hjk <hjk@theqtcompany.com>

src/plugins/coreplugin/dialogs/newdialog.cpp

@@ -471,8 +471,7 @@ void NewDialog::accept()
     saveState();
     if (m_ui->templatesView->currentIndex().isValid()) {
         IWizardFactory *wizard = currentWizardFactory();
-        QTC_CHECK(wizard);
-        if (wizard) {
+        if (QTC_GUARD(wizard)) {
             QTimer::singleShot(0, std::bind(&runWizard, wizard, m_defaultLocation,
                                             selectedPlatform(), m_extraVariables));
         }