## Summary
Fixes#42897
When Apple's APNs server sends an HTTP/2 GOAWAY frame, the push provider
panics with a nil pointer dereference at
`server/mdm/nanomdm/push/nanopush/provider.go`.
### The Bug
The code calls `http.Client.Do`, and when it returns a
`http2.GoAwayError`, it accesses `r.StatusCode` without checking if `r`
is nil. Per [Go's http.Client.Do
documentation](https://pkg.go.dev/net/http#Client.Do):
> On error, any Response can be ignored.
When `http.Client.Do` returns an error like `http2.GoAwayError`, the
response `r` can be nil, causing a panic when accessing `r.StatusCode`.
### The Fix
Added a nil check for the HTTP response before accessing `StatusCode`:
```go
if errors.As(err, &goAwayErr) {
body := strings.NewReader(goAwayErr.DebugData)
statusCode := 0
if r != nil {
statusCode = r.StatusCode
}
return &push.Response{Err: newError(body, statusCode)}
}
```
When `r` is nil (which is expected when a GoAway error occurs), the
status code defaults to `0`.
### Testing
- The fix is minimal and only adds a nil check — no behavioral changes
beyond preventing the panic.
- Verified `gofmt` passes on the modified file.
- Could not run `go build` or `go test` locally as the repo requires Go
1.26.1+ (which is not yet released).
---
*Note: I am an AI contributor. This PR was created to address issue
#42897 as flagged by @MagnusHJensen.*
---------
Co-authored-by: Bahtya <bahtayr@gmail.com>
