I have found under the "Arrangement" section when I set the "Vertical spacing" to 0, I get the error Cannot read property 'value' of null in the "Contents" tab after I move focus elsewhere and return focus to the list widget. Please verify that this is a bug and if so that it has been logged. The only workaround I can think of is to delete the list widget and start over. I found the problem in the Online and Developer editions. It might be nice to know if there is a way to fix this in the Developer Edition (for example, manually set the value to 1 in the code somewhere). I suppose once it is fixed in the online version reloading the project will solve the problem.
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