fixes server error when searching for parcel keyword only (parzelle,

see #925 

When searching for "parzelle" only [1] there is the following error:
```
[Mon Aug 11 07:23:46 2014] [error] [client 10.35.188.159]   File "/var/www/vhosts/mf-chsdi3/private/chsdi/chsdi/views/search.py", line 113, in _swiss_search
[Mon Aug 11 07:23:46 2014] [error] [client 10.35.188.159]     temp = self.sphinx.Query(searchTextFinal, index='swisssearch')
[Mon Aug 11 07:23:46 2014] [error] [client 10.35.188.159] UnboundLocalError: local variable 'searchTextFinal' referenced before assignment
```
@loicgasser please have a look at this pr, i could not find any side-effect.


[1] http://api3.geo.admin.ch/rest/services/api/SearchServer?searchText=parzelle&type=locations