Exception when JITTER performed on empty field

[wetzelj]

When a JITTER rule is performed on a header field which contains an empty string rather than a DICOM formatted date/timestamp value, an exception occurs, stopping the deidentification of the header.

Cause:

• On parser.py line 467, jitter_timestamp() is called to obtain the new value for the timestamp field. This function then calls get_timestamp(), which actually calculates the new value. In get_timestamp(), if the value is "" or None, the new value returned is None.
• Subsequently, on parser.py line 468, replace_field() is called with the new "None" value. Within replace_field, we eventually get to the parse_field() method. Parse field attempts to perform a regex search (to look for potential expanders) on the None value, causing the exception.

Proposed Fix:

• For JITTER actions, check the new value returned for the field. Only call replace_field if the value is not None. (pull request coming shortly)

[vsoch]

Sounds good!