runtime error: invalid memory address or nil pointer dereference

v1.7.7

2022/06/30 09:36:28 http: panic serving 127.0.0.1:35814: runtime error: invalid memory address or nil pointer dereference
goroutine 2786 [running]:
net/http.(*conn).serve.func1()
        net/http/server.go:1802 +0xb9
panic({0x7faa80, 0xba68b0})
        runtime/panic.go:1047 +0x266
github.com/jpillora/chisel/server.(*Server).handleWebsocket(0xc0000a8320, {0x8fff80, 0xc00019c460}, 0xc00010ae00)
        github.com/jpillora/chisel/server/server_handler.go:94 +0x463
github.com/jpillora/chisel/server.(*Server).handleClientHandler(0xc0000a8320, {0x8fff80, 0xc00019c460}, 0xc00010ae00)
        github.com/jpillora/chisel/server/server_handler.go:24 +0x129
net/http.HandlerFunc.ServeHTTP(0x0, {0x8fff80, 0xc00019c460}, 0x46204e)
        net/http/server.go:2047 +0x2f
net/http.serverHandler.ServeHTTP({0xc00037f860}, {0x8fff80, 0xc00019c460}, 0xc00010ae00)
        net/http/server.go:2879 +0x43b
net/http.(*conn).serve(0xc00007c280, {0x9021a0, 0xc0000720c0})
        net/http/server.go:1930 +0xb08
created by net/http.(*Server).Serve
        net/http/server.go:3034 +0x4e8

Start by reading server/server_handler.go, especially Server.handleWebsocket at line 94, using the supplied stack trace as the entry point. Reproduce the panic if possible and determine which request path triggers it. Done means the same request no longer causes a nil pointer panic and the relevant behavior is covered by a regression test.