Fix UnsupportedOperationException

Create new user and access to dashboard/issues/repos.

```
HTTP ERROR 500

Problem accessing /dashboard/issues/repos. Reason:

    empty.reduceLeft
Caused by:

java.lang.UnsupportedOperationException: empty.reduceLeft
	at scala.collection.LinearSeqOptimized$class.reduceLeft(LinearSeqOptimized.scala:124)
	at scala.collection.immutable.List.reduceLeft(List.scala:84)
	at service.IssuesService$$anonfun$searchIssueQuery$1.apply(IssuesService.scala:164)
	at service.IssuesService$$anonfun$searchIssueQuery$1.apply(IssuesService.scala:160)
	at scala.slick.lifted.Query.filter(Query.scala:37)
	at service.IssuesService$class.searchIssueQuery(IssuesService.scala:160)
	at service.IssuesService$class.searchIssue(IssuesService.scala:119)
	at app.DashboardController.searchIssue(DashboardController.scala:6)
	at app.DashboardControllerBase$class.app$DashboardControllerBase$$searchIssues(DashboardController.scala:43)
	at app.DashboardControllerBase$$anonfun$1$$anonfun$apply$1.apply(DashboardController.scala:14)
...
```