Issue search not working properly (BB-4021)

For [[https://bitbucket.org/tortoisehg/thg/issues|TortoiseHg]] there are several issues containing the words "TypeError" and "NoneType" (like [[https://bitbucket.org/tortoisehg/thg/issue/1838/|thg BCLOUD-1838]]), yet the search for both words (separated by a space) give in no results:

https://bitbucket.org/tortoisehg/thg/issues?q=TypeError+NoneType

This occurs if you have one key word in either the title or the description but not both.

This is quite bad as this leads to a [[https://bitbucket.org/tortoisehg/thg/issue/1617/crash-when-going-to-settings-on-new|lot of duplicate issues]] and therefore unnecessary work for the developers.