Hotfix/6.1.7

Fixed crash:
```
#0 /usr/local/sitefusion/class/customTree.php.inc(114): errorHandler(8, 'Undefined offse...', '/usr/local/site...', 114, Array)
#1 [internal function]: XULCustomTree->treeDropHandler(Object(Event), Object(XULCustomTree), '100', 23, 0)
#2 /usr/local/sitefusion/sys/xulNode.php.inc(451): call_user_func_array(Array, Array)
#3 /usr/local/sitefusion/daemon/app.php.inc(345): Node->commandHandler('treeDrop', Array)
#4 /usr/local/sitefusion/daemon/app.php.inc(203): ApplicationProcess::HandleComm(Resource id #20452, Object(stdClass))
#5 /usr/local/sitefusion/daemon/app.php.inc(137): ApplicationProcess::ApplicationLoop()
#6 /usr/local/sitefusion/daemon/daemon.php.inc(896): ApplicationProcess::StartServer(Resource id #20278, Resource id #20280, Resource id #20282, Object(stdClass), 5176, 'wxvimdnwxrkcocb...')
#7 /usr/local/sitefusion/daemon/daemon.php.inc(495): DaemonProcess::StartApplication(Resource id #20278, 'wxvimdnwxrkcocb...')
#8 /usr/local/sitefusion/daemon/daemon.php.inc(341): DaemonProcess::HandleClient(Resource id #20278)
#9 /usr/local/sitefusion/daemon/daemon.php.inc(122): DaemonProcess::MainLoop()
#10 /usr/local/sitefusion/daemon/start.php(43): DaemonProcess::StartServer(Array)
#11 {main}
```