Fatal error: Unsupported operand types field_extrawidgets.module on line 119

I get the same error whenever I try to save a content type containing a field marked hidden. The content type is save correctly but after pressing Save I get a WSOD.

PHP Fatal error: Unsupported operand types in /.../sites/all/modules/field_extrawidgets/field_extrawidgets.module on line 119

Please help

The problem is:

$formatter_settings += field_info_formatter_settings($formatter_type);

should be

$formatter_settings .= field_info_formatter_settings($formatter_type);

Please correct and commit.
Thanks in advance

Can you give me a clear way to reproduce this?

Marking this as duplicate of #1305268: Contents of a read-only field is hidden on the term/entity edit form, and thus cannot be edited. patch in #1305268-3: Contents of a read-only field is hidden on the term/entity edit form, and thus cannot be edited. solves the issue