Hide SQL errors on Space Used from Admin tools when not using MySQL DB

1. Open an instance of XE 7.4 with IE11
2. Install Filesystem attachment: http://test.xwiki.org/xwiki/bin/view/Other+Tests/Enable+Filesystem+Attachment+Store
3. Install admin tools app and go to http://localhost:8080/xwiki/bin/view/Admin/UsedSpace
4. Keep the default HSQLDB

Actual result:

• Because you are not using HSQLDB, you get these sql errors:
  Error running sql: select sum(round(data_length/1024/1024,2)) as 'xwikirecyclebin' from information_schema.tables where table_name='xwikirecyclebin' and table_schema='xwiki';
  unexpected token: xwikirecyclebin

Error running sql: select sum(round(data_length/1024/1024,2)) as 'xwikircs' from information_schema.tables where table_name='xwikircs' and table_schema='xwiki';
unexpected token: xwikircs

Expected result:

• Keep only this warning:
  Your database is: HSQL Database Engine
  HSQL Database Engine is not supported for this action

• Hide the sql errors