RE #27188 Fix validation if custom selected then closed

If custom spectra was selected from the dropdown and then the tick box
was deselected, the GUI would still check the validity of the spectrum
numbers. As this was usually empty, the calibration would fail to run.

scripts/Engineering/gui/engineering_diffraction/tabs/calibration/presenter.py

@@ -125,7 +125,7 @@ class CalibrationPresenter(object):
         if not self.validate_run_numbers():
             create_error_message(self.view, "Check run numbers/path is valid.")
             return False
-        if not self.cropping_widget.is_valid():
+        if self.view.get_crop_checked() and not self.cropping_widget.is_valid():
             create_error_message(self.view, "Check cropping values are valid.")
             return False
         return True