When KDevPluginController::query() was called with empty constrain it
were resulting in incorrect query string being passed to TDETrader,
which were resulting in at least warnings like the next one:
```
[tdeio (TDETrader)] [6751] WARNING: Parsing ' and [X-TDevelop-Version] == 5' gave syntax error
```
Signed-off-by: Alexander Golubev <fatzer2@gmail.com>
(cherry picked from commit c8d7b46522)
This enables compilation under both Qt3 and Qt4
git-svn-id: svn://anonsvn.kde.org/home/kde/branches/trinity/kdevelop@1236710 283d02a7-25f6-0310-bc7c-ecb5cbfe19da