[BUG] BIDSpath.update changes suffix option even if suffix isn't supported

[teonbrooks]

Describe the bug

When using the BIDSPath option, if you try to update the suffix with a non-supported suffix (e.g. _ave), you will receive an error that the suffix is not supported (intended behavior) but the BIDSPath option is updated regardless (not intended behavior). I believe this is because the _check method is called after setting the suffix instead of being called first.

Steps to reproduce

import mne_bids


bids_path = mne_bids.BIDSPath(subject='test')
bids_path.update(suffix='ave')
bids_path

Expected results

BIDSPath object should not update with the unsupported extension or there should be an ignore option so that the error doesn't occur.

Actual results

In [6]: bids_path.update(suffix='ave')  
ValueError: Suffix ave is not allowed. Use one of these suffixes ['meg', 'markers', 'eeg', 'ieeg', 'T1w', 'FLASH', 'participants', 'scans', 'electrodes', 'channels', 'coordsystem', 'events', 'headshape', 'digitizer', 'beh', 'physio', 'stim'].

In [7]: bids_path                                                               
Out[7]: 
BIDSPath(
root: None
datatype: None
basename: sub-test_ave)