Search will always fail after entering "Error: File not found!" page

[amotzte]

After getting to "Error: File not found!" page all searches would failed from this page.

Reproduce:

• Go to file not found page (for example /source/xref/filenotfound)
• Select a project and try to search for a valid string

Observed

• Page is redirected to "Error: File not found!" again (Regardless of if search should be found or not)

Version:f8419a9 prepare for 0.13-rc4

UPDATE:
It seems that if doing search from "File not found" page then the url is
/source/xref/search?q=...
Indead of
/source/search?q=...