Check job before removing it

Change-Id: Ibbd4da25fac6016a0d76c8f810ac567f6fd075f1
Closes-Bug: #1782731

watcher/decision_engine/audit/continuous.py

@@ -62,10 +62,11 @@ class ContinuousAuditHandler(base.AuditHandler):
         if objects.audit.AuditStateTransitionManager().is_inactive(audit):
             # if audit isn't in active states, audit's job must be removed to
             # prevent using of inactive audit in future.
-            if self.scheduler.get_jobs():
-                [job for job in self.scheduler.get_jobs()
-                 if job.name == 'execute_audit' and
-                 job.args[0].uuid == audit.uuid][0].remove()
+            jobs = [job for job in self.scheduler.get_jobs()
+                    if job.name == 'execute_audit' and
+                    job.args[0].uuid == audit.uuid]
+            if jobs:
+                jobs[0].remove()
             return True
 
         return False