[Bug] Crash when deleting an online node

[nblock]

Is this a support request?

• This is not a support request

Is there an existing issue for this?

• I have searched the existing issues

Current Behavior

A panic occurs when an online node is deleted:

2024-09-09T19:50:58+02:00 INF github.com/juanfont/headscale/hscontrol/auth.go:28 > Successfully sent auth url: http://headscale.lan:8080/register/mkey:622647d93d72d3edf2bff8d179495dd99243a8a75e631250b17d62a40029b712 expiry=-62135596800 fo
llowup=http://headscale.lan:8080/register/mkey:622647d93d72d3edf2bff8d179495dd99243a8a75e631250b17d62a40029b712 machine_key=[YiZH2] node=DESKTOP-T8CLBV9 node_key=[8WSlh] node_key_old=
2024-09-09T19:50:58+02:00 DBG New noise client cap_ver=104 handler=/key  
2024-09-09T19:50:58+02:00 DBG github.com/juanfont/headscale/hscontrol/auth.go:596 > Client is registered and we have the current NodeKey. All clear to /map node=DESKTOP-T8CLBV9
2024-09-09T19:50:58+02:00 INF github.com/juanfont/headscale/hscontrol/auth.go:627 > Node successfully authorized node=DESKTOP-T8CLBV9
2024-09-09T19:50:58+02:00 INF github.com/juanfont/headscale/hscontrol/poll.go:698 > node has connected, mapSession: 0xc0001a2480, chan: 0xc0001fb810 node=DESKTOP-T8CLBV9 node.id=3 omitPeers=false readOnly=false stream=true
2024-09-09T19:51:48+02:00 ERR github.com/juanfont/headscale/hscontrol/poll.go:718 > Could not get machine from db error="record not found" node=DESKTOP-T8CLBV9 node.id=3 omitPeers=false readOnly=false stream=true
2024/09/09 19:51:48 http2: panic serving 192.168.191.238:54790: runtime error: invalid memory address or nil pointer dereference
goroutine 2050 [running]:                                                                                              
golang.org/x/net/http2.(*serverConn).runHandler.func1()                                                                
        golang.org/x/net@v0.28.0/http2/server.go:2407 +0x145
panic({0x1dadb00?, 0x34d2a30?})                      
        runtime/panic.go:785 +0x132                      
github.com/juanfont/headscale/hscontrol.(*mapSession).serveLongPoll.func1()
        github.com/juanfont/headscale/hscontrol/poll.go:206 +0x8a
github.com/juanfont/headscale/hscontrol.(*mapSession).serveLongPoll(0xc0001a2480)
        github.com/juanfont/headscale/hscontrol/poll.go:290 +0x11f4
github.com/juanfont/headscale/hscontrol.(*noiseServer).NoisePollNetMapHandler(0xc000589290, {0x2464940, 0xc00038ca80}, 0xc000266780)
        github.com/juanfont/headscale/hscontrol/noise.go:240 +0x365
net/http.HandlerFunc.ServeHTTP(0xaad78?, {0x2464940?, 0xc00038ca80?}, 0xc000290cf0?)
        net/http/server.go:2220 +0x29
github.com/juanfont/headscale/hscontrol.prometheusMiddleware.func1({0x2464940, 0xc00038ca80}, 0xc000266780)
        github.com/juanfont/headscale/hscontrol/metrics.go:87 +0x143
net/http.HandlerFunc.ServeHTTP(0xc000266640?, {0x2464940?, 0xc00038ca80?}, 0x7fb68785b5b8?)
        net/http/server.go:2220 +0x29
github.com/gorilla/mux.(*Router).ServeHTTP(0xc0006120c0, {0x2464940, 0xc00038ca80}, 0xc000266500)
        github.com/gorilla/mux@v1.8.1/mux.go:212 +0x1e2
golang.org/x/net/http2.(*serverConn).runHandler(0x44951b?, 0xc00052bae0?, 0x24674f0?, 0xc00052bdb0?)
        golang.org/x/net@v0.28.0/http2/server.go:2414 +0xf5 
created by golang.org/x/net/http2.(*serverConn).scheduleHandler in goroutine 1960
        golang.org/x/net@v0.28.0/http2/server.go:2348 +0x21d
2024-09-09T19:51:48+02:00 ERR Failed to fetch node from the database with node key: nodekey:f164a587d1b77539def9790a4085e950556f231d25e9f8dec125c121d7d6c46c handler=NoisePollNetMap
2024-09-09T19:51:48+02:00 ERR Failed to fetch node from the database with node key: nodekey:f164a587d1b77539def9790a4085e950556f231d25e9f8dec125c121d7d6c46c handler=NoisePollNetMap
2024-09-09T19:51:48+02:00 ERR Failed to fetch node from the database with node key: nodekey:f164a587d1b77539def9790a4085e950556f231d25e9f8dec125c121d7d6c46c handler=NoisePollNetMap

Expected Behavior

The node should be removed and headscale should not crash.

Steps To Reproduce

• Connect a new node with headscale; headscale nodes list shows the as "online"
• Delete the node: headscale nodes delete -i ID

Environment

- OS: Debian 12
- Headscale version: v0.23.0-beta.4 (but also seen earlier today with beta3)
- Tailscale version: 1.72.0

Runtime environment

• Headscale is behind a (reverse) proxy
• Headscale runs in a container

Anything else?

No response