indexargs_url produces a url using information from 
two sources; the parameters from the current request, 
and the parameters of that indexargs_url method. The 
call to indexargs_url for "Show Unassigned" and "Show 
All" fails to override any search_text. This leads to 
the following unexpected scenario:

a. Type some text in the top-right search box, and 
press the search button.
b. You see a subset of all issue; only those matching 
that search.
c. Click on "all issues".
d. You expect to see everything, but actually see the 
same subset from b.

The attached patch fixes this by explictly clearing 
search_text in those two calls to indexargs_url.

This patch also includes two less critical changes:

a. Include the requested search_text as the default 
value for the search input control. The current 
behaviour always leaves this control blank. This is 
handy as a reminder about what you searched for, and 
for refining searches.

b. I changed the 'Your Actions' link to use 
indexargs_url, for consistency.