Added logic to limit maximum font point size for Qt Family Keyboard Text. Prevents crash if user enters an excessive value.

src/drivers/Qt/FamilyKeyboard.cpp

@@ -849,6 +849,10 @@ void FKBConfigDialog::openFontDialog(void)
 
 	if ( ok )
 	{
+		if ( selFont.pointSize() > 72 )
+		{
+			selFont.setPointSize(72);
+		}
 		keyboard->setFont( selFont );
 		keyboard->update();