qt: Ignore showNormalIfMinimized in initialization or shutdown

Also get rid of ui_interface flag NOSHOWGUI. It's up to the GUI to
decide this.

Fixes #4360.

src/qt/bitcoingui.cpp

@@ -780,11 +780,7 @@ void BitcoinGUI::message(const QString &title, const QString &message, unsigned
         if (!(buttons = (QMessageBox::StandardButton)(style & CClientUIInterface::BTN_MASK)))
             buttons = QMessageBox::Ok;
 
-        // Ensure we get users attention, but only if main window is visible
-        // as we don't want to pop up the main window for messages that happen before
-        // initialization is finished.
-        if(!(style & CClientUIInterface::NOSHOWGUI))
-            showNormalIfMinimized();
+        showNormalIfMinimized();
         QMessageBox mBox((QMessageBox::Icon)nMBoxIcon, strTitle, message, buttons, this);
         int r = mBox.exec();
         if (ret != NULL)
@@ -921,6 +917,8 @@ void BitcoinGUI::setEncryptionStatus(int status)
 
 void BitcoinGUI::showNormalIfMinimized(bool fToggleHidden)
 {
+    if(!clientModel)
+        return;
     // activateWindow() (sometimes) helps with keyboard focus on Windows
     if (isHidden())
     {