Error when adding a blank reference sample to a worksheet

[ramonski]

Description

Error happens when adding a blank reference sample to a worksheet

Reproduction guide

1. Create a worksheet
2. Add a blank reference sample

Observed behaviour

Traceback occurs when trying to add a blank to a worksheet.

Expected behaviour

Adding a blank works for worksheets.

Versions

• OS: Linux

• senaite.core: 2.x

• senaite.impress: 2.x

• senaite.core.listing: 2.x

• senaite.core.supermodel: 2.x

Traceback

2020-11-02T20:11:35 ERROR Zope.SiteErrorLog 1604344295.170.324558837311 https://senaite.ridingbytes.com/worksheets/WS-001/add_blank
Traceback (innermost last):
  Module ZServer.ZPublisher.Publish, line 144, in publish
  Module ZPublisher.mapply, line 85, in mapply
  Module ZServer.ZPublisher.Publish, line 44, in call_object
  Module bika.lims.browser.worksheet.views.referencesamples, line 112, in __call__
  Module bika.lims.browser.worksheet.views.referencesamples, line 134, in handle_submit
AttributeError: 'NoneType' object has no attribute 'get'```

## Screenshot