autoupdater: fix: nil pointer dereference on non status graphQL error

If a GitHub GraphQL endpoint returned an error that is not an HTTP status error,
wrapGraphQLRetryableErrors() returned nil instead of the passed error.

This caused that Client.ReadyForMergeStatus() returned (nil,nil) and a nil
pointer deference was done in the autoupdater.

This fixes:
	panic: runtime error: invalid memory address or nil pointer dereference
	[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x9293f6]
	goroutine 40 [running]:
	github.com/simplesurance/goordinator/internal/autoupdate.(*queue).updatePR(0xc0001e68f0, {0xc5b498, 0xc0000ae500}, 0xc00055e0a0)
	        github.com/simplesurance/goordinator/internal/autoupdate/queue.go:500 +0x476
	github.com/simplesurance/goordinator/internal/autoupdate.(*queue).scheduleUpdate.func1()
	        github.com/simplesurance/goordinator/internal/autoupdate/queue.go:422 +0xd4
	github.com/simplesurance/goordinator/internal/autoupdate/routines.(*Pool).worker(0xc00042eea0)
	        github.com/simplesurance/goordinator/internal/autoupdate/routines/pool.go:92 +0x75
	created by github.com/simplesurance/goordinator/internal/autoupdate/routines.NewPool
	        github.com/simplesurance/goordinator/internal/autoupdate/routines/pool.go:39 +0x133

internal/autoupdate/queue.go

@@ -500,8 +500,8 @@ func (q *queue) updatePR(ctx context.Context, pr *PullRequest) {
 		logfields.ReviewDecision(status.ReviewDecision),
 		logfields.StatusCheckRollupState(status.StatusCheckRollupState),
 	)
-	if status.ReviewDecision != githubclt.ReviewDecisionApproved {
 
+	if status.ReviewDecision != githubclt.ReviewDecisionApproved {
 		if err := q.Suspend(pr.Number); err != nil {
 			logger.Error(
 				"suspending PR because it is not approved, failed",

internal/githubclt/client.go

@@ -369,7 +369,7 @@ var graphQlHTTPStatusErrRe = regexp.MustCompile(`^non-200 OK status code: ([0-9]
 func (clt *Client) wrapGraphQLRetryableErrors(err error) error {
 	matches := graphQlHTTPStatusErrRe.FindStringSubmatch(err.Error())
 	if len(matches) != 2 {
-		return nil
+		return err
 	}
 
 	errcode, atoiErr := strconv.Atoi(matches[1])

internal/githubclt/client_test.go

@@ -2,6 +2,7 @@ package githubclt
 
 import (
 	"context"
+	"errors"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -37,3 +38,9 @@ func TestWrapRetryableErrorsGraphql(t *testing.T) {
 	var retryableErr *goorderr.RetryableError
 	assert.ErrorAs(t, err, &retryableErr)
 }
+
+func TestWrapRetryableErrorsGraphqlWithNonStatusErr(t *testing.T) {
+	err := errors.New("error")
+	wrappedErr := (&Client{}).wrapGraphQLRetryableErrors(err)
+	assert.Equal(t, err, wrappedErr)
+}