Go to link on search page is broken

[MrGecko]

Describe the bug The Go to link on the search page is broken when one of the filter is set to None

AttributeError: 'NoneType' object has no attribute 'replace'

The faulty line in app/utils/forms.py", line 65, in column_search_filter:

value = value.replace('¤$¤', '*')

To Reproduce Steps to reproduce the behavior:

1. Go to the search page
2. Click on the Go to link

Expected behavior The empty filter should be ignored earlier in the search algorithm