[core] fix nil task access

Fixes nil access issue introduced by myself in #647

Author: knopers8

core/task/manager.go

@@ -953,11 +953,13 @@ func (m *Manager) GetTask(id string) *Task {
 
 func (m *Manager) updateTaskState(taskId string, state string) {
 	taskPtr := m.roster.getByTaskId(taskId)
-	if taskPtr == nil && state != "DONE" {
-		log.WithField("taskId", taskId).
-			WithField("state", state).
-			WithField(infologger.Level, infologger.IL_Support).
-			Warn("attempted state update of task not in roster")
+	if taskPtr == nil {
+		if state != "DONE" {
+			log.WithField("taskId", taskId).
+				WithField("state", state).
+				WithField(infologger.Level, infologger.IL_Support).
+				Warn("attempted state update of task not in roster")
+		}
 		return
 	}