fix nil deference for all API callers

.changelog/13845.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+api: Fixed a nil pointer dereference when periodic jobs are missing their periodic spec
+```

api/jobs.go

@@ -822,7 +822,7 @@ func (p *PeriodicConfig) Canonicalize() {
 // returned. The `time.Location` of the returned value matches that of the
 // passed time.
 func (p *PeriodicConfig) Next(fromTime time.Time) (time.Time, error) {
-	if *p.SpecType == PeriodicSpecCron {
+	if p != nil && *p.SpecType == PeriodicSpecCron {
 		e, err := cronexpr.Parse(*p.Spec)
 		if err != nil {
 			return time.Time{}, fmt.Errorf("failed parsing cron expression %q: %v", *p.Spec, err)

command/job_run.go

@@ -349,9 +349,6 @@ func (c *JobRunCommand) Run(args []string) int {
 
 	evalID := resp.EvalID
 
-	// #13844: canonicalize the job in case it was a partial API definition
-	job.Canonicalize()
-
 	// Check if we should enter monitor mode
 	if detach || periodic || paramjob || multiregion {
 		c.Ui.Output("Job registration successful")