Make Verify more tolerant of errors

Verify should be more tolerant of errors, or at least provide meaningful error information, such as segment number.

In a large document, such a general error message is very difficult to find. Error dialog box in Trados Studio with a red 'X' icon, displaying the message 'Failed to verify document: Object reference not set to an instance of an object.' with 'Knowledge Base' and 'Community' links and an 'OK' button.