Bugfix on TsdFrame getitem

[BalzaniEdoardo]

On TsdFrame of 1 column, this would cause an error:

tsdframe = nap.TsdFrame(t=np.arange(10), d=np.ones((10, 1)))
tsdframe[0]

Since in the getitem it was checking if key[1] is list or array but key is an integer in this case.

Fixed it quickly and added a test for this 1 column tsdframe.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files with missing lines	Coverage Δ
pynapple/core/time_series.py	89.82% <100.00%> (+0.05%)	⬆️