neonvm-controller: Fix error in panic catching middleware

[sharnoff]

While working on #963, I spotted this in the logs:

{"level":"dpanic","ts":"2024-06-15T18:50:47.809Z","msg":"odd number of arguments passed as key-value pairs for logging",...,"ignored key":"goroutine 501 [running]:\nruntime/debug.Stack()\n\t/usr/local/go/src/runtime/debug/stack.go:24 ..."}