Make sure that print label dialog has a submit button. (#4240)

Steps to reproduce problem:
Go to a screen that has a modal without a submit button like "Show QR code" of the Sublocation overview.
Close the QR code modal and after that go to the "Print label" option.
It will no longer show a submit button.

InvenTree/templates/js/translated/label.js

@@ -321,6 +321,7 @@ function selectLabel(labels, items, options={}) {
     });
 
     modalEnable(modal, true);
+    modalShowSubmitButton(modal, true);
     modalSetTitle(modal, '{% trans "Select Label Template" %}');
     modalSetContent(modal, html);