fix(mobile): fix text search

[johnstef99]

Fixes #14814

[johnstef99]

This commit f59b813 changed how SearchFilter.copyWith handles null value for context and filename but this created this bug #14814 where when you apply other filters the context and filename always get turned into null.

Passing empty string at the context or the filename filter is necessary to remove the filter when the user submits the search field with no text. The SearchService handles it by checking if the strings context and filename are empty.

I think this answers both of the above questions.

[alextran1502]

Can you please write down some functional test cases and how you verified that they are fixed with this change?

[johnstef99]

Can you please write down some functional test cases and how you verified that they are fixed with this change?

sure I will write some tests to verify that the search is working as inteded. If these tests existed this commit f59b813 would have failed them.