The problem is that you are performing your operations within the blueprint library itself.
Your “Options Main” is a local variable, it only exists in the scope of this function. Due to this reason, your check for it will always return invalid because the object was never created.
If you want to use a blueprint library for the purpose of populating a widget with information, you need to give the widget reference as input to this function. That way, after you call your “Create Widget” method for “Options Menu”, you feed the result to your “Fill combobox with resolutions” function. Give your function a return of widget as well, that way you get the modified widget to add to viewport.
Hope that helps 