When portal_contributions.PUT() is called, Document was not converted (and `base_data`
was not set) by document_conversion_interaction_workflow as this was only done on
_set{Data,File}() and OFS.Image.update_data() sets `data` property directly.

This fixes failures on testWebDavSupport.test_GET_on_{contributionTool,document}
with erp5_full_text_*_catalog bt5 installed: SQLCatalog_deferFullTextIndexActivity
Activity failing with `NotConvertedError` when trying to convert to txt as
`base_data` is not set.