ddl: fix invailid ddl job panic (#7940)

ddl/ddl_worker.go

@@ -510,7 +510,7 @@ func (w *worker) runDDLJob(d *ddlCtx, t *meta.Meta, job *model.Job) (ver int64,
 	default:
 		// Invalid job, cancel it.
 		job.State = model.JobStateCancelled
-		err = errInvalidDDLJob.GenWithStack("invalid ddl job %v", job)
+		err = errInvalidDDLJob.GenWithStack("invalid ddl job type: %v", job.Type)
 	}
 
 	// Save errors in job, so that others can know errors happened.

ddl/ddl_worker_test.go

@@ -136,6 +136,24 @@ func (s *testDDLSuite) TestTableError(c *C) {
 
 }
 
+func (s *testDDLSuite) TestInvalidDDLJob(c *C) {
+	store := testCreateStore(c, "test_invalid_ddl_job_type_error")
+	defer store.Close()
+	d := testNewDDL(context.Background(), nil, store, nil, nil, testLease)
+	defer d.Stop()
+	ctx := testNewContext(d)
+
+	job := &model.Job{
+		SchemaID:   0,
+		TableID:    0,
+		Type:       model.ActionNone,
+		BinlogInfo: &model.HistoryInfo{},
+		Args:       []interface{}{},
+	}
+	err := d.doDDLJob(ctx, job)
+	c.Assert(err.Error(), Equals, "[ddl:3]invalid ddl job type: none")
+}
+
 func (s *testDDLSuite) TestForeignKeyError(c *C) {
 	store := testCreateStore(c, "test_foreign_key_error")
 	defer store.Close()