Bugfix for empty trigger tables

[eagoetz]

This PR fixes the empty table where we want to extend the columns. There was a bug when using extend('foo'). It should be extend(['foo']).

[codecov[bot]]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (21b3e62) 49.64% compared to head (76c39fd) 49.64%.

Files	Patch %	Lines
gwsumm/triggers.py	0.00%	2 Missing :warning:

Additional details and impacted files

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[iaraota]

@eagoetz I approved the PR, but could you explain me why you are using .extend([item]) instead of .append(item)?

[eagoetz]

@eagoetz I approved the PR, but could you explain me why you are using .extend([item]) instead of .append(item)?

@iaraota In general, I prefer extend() over append() because, for example,

>>> foo = [1, 2]
>>> foo.append([3, 4])
>>> foo
[1, 2, [3, 4]]
>>> bar = [1, 2]
>>> bar.extend([3, 4])
>>> bar
[1, 2, 3, 4]

I agree that it's perhaps not necessary in this case, but I like this behviour better (when I don't screw it up like I did here).