Detect time entries with a task but no project in consistency check

The comparison used != which evaluates to NULL when the time entry has no
project, so entries that kept their task after the project was removed
were not reported.

app/Console/Commands/SelfHost/SelfHostDatabaseConsistency.php

@@ -39,7 +39,7 @@ class SelfHostDatabaseConsistency extends Command
         $problems = DB::table('time_entries')
             ->select(['time_entries.id as id'])
             ->join('tasks', 'time_entries.task_id', '=', 'tasks.id')
-            ->where('tasks.project_id', '!=', DB::raw('time_entries.project_id'))
+            ->whereRaw('tasks.project_id is distinct from time_entries.project_id')
             ->get();
         $this->logProblems($problems, 'Time entries have a task that does not belong to the project of the time entry', $hadAProblem);