Steps to reproduce

1. Create a uploadField dialog without adding an allowedMimeTypePattern (According to https://docs.magnolia-cms.com/product-docs/6.2/Templating/Dialog-definition/Field-definition/List-of-fields/Upload-field.html#_common_upload_field_properties it is optional!)
2. Upload any file
3. A NPE is thrown:
4. The file is uploaded and can be used anyway

Expected results

It's still possible to use the uploadField without defining an allowedMimeTypePattern and no error is thrown!

Actual results

The uploadField can be used without defining an allowedMimeTypePattern and a NPE error is thrown.

Workaround

Define an allowedMimeTypePattern on all uploadFields that don't have one yet!

Development notes

This Bug was introduced with https://jira.magnolia-cms.com/browse/MGNLUI-6894