Crash when finishing the editing of an undefined end time

[tanius]

I think this is the first time that tom-ui crashed on me, which speaks for its quality :) The crash is reproducible as follows:

1. Start a new timeframe in any project or sub-project.
2. Double-click into the "End" field of the new timeframe. It will show an edit box with "01.01.00 00:00" in it.
3. Click anywhere outside the edit box, as if to leave it. This leads to a crash.

In step 3, pressing Esc or Return does not lead to a crash and rather leads to the respective expected results.

(As a side note, it could be more practical to initialize the edit box with the current date and time rather than "01.01.00 00:00". The user can then adjust this to a date and time in the recent past with minimal effort, which is probably the most frequent use case when editing an end time of a currently active timeframe.)

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Some technical information about the crash, sadly as a screenshot as I cannot figure out how to copy stuff from the apport crash-report window: