panic on apple m1 (nil pointer)

[meowsbits]

An error in the core-geth tests happens on Apple M1 architecture.
The backtrace points to https://github.com/etclabscore/go-openrpc-reflect/blob/master/common.go#L372.

cc @ziogaschr @diega

--- FAIL: TestRPCDiscover (0.02s)
    ethclient_test.go:760: method handler crashed
INFO [08-23|14:31:19.398] Persisted trie from memory database      nodes=1 size=146.00B time="2.583µs"  gcnodes=0 gcsize=0.00B gctime=0s livenodes=1  livesize=0.00B
WARN [08-23|14:31:19.399] Sanitizing invalid miner gas price       provided=<nil> updated=1,000,000,000
INFO [08-23|14:31:19.399] Allocated trie memory caches             clean=0.00B dirty=0.00B
INFO [08-23|14:31:19.399] Writing custom genesis block 
[...]
WARN [08-23|14:31:19.378] Sanitizing invalid gasprice oracle max block history provided=0     updated=1
WARN [08-23|14:31:19.378] Error reading unclean shutdown markers   error="not found"
INFO [08-23|14:31:19.378] Starting peer-to-peer node               instance=CoreGeth/darwin-arm64/go1.18.1
INFO [08-23|14:31:19.379] Imported new chain segment               blocks=2 txs=2 mgas=0.042 elapsed="369.583µs" mgasps=113.642 number=2 hash=4bab76..d2d838 age=53y4mo3w dirty=1.62KiB
INFO [08-23|14:31:19.380] New local node record                    seq=1,661,254,279,379 id=534093df1652cfed ip=127.0.0.1 udp=60777 tcp=0
INFO [08-23|14:31:19.380] Started P2P networking                   self="enode://19bad38415be0fc06add3f32ed62e8890f0bccde8f84eff33c6079678b2a29fedff295ea7ce954838f6695765af55fff6bbb4c2f57b0fe06deea61ab02346fff@127.0.0.1:0?discport=60777"
ERROR[08-23|14:31:19.397] RPC method rpc.discover crashed: runtime error: invalid memory address or nil pointer dereference
goroutine 528 [running]:
github.com/ethereum/go-ethereum/rpc.(*callback).call.func1()
        /Users/ziogaschr/Sites/go/src/github.com/etclabscore/core-geth/rpc/service.go:199 +0x74
panic({0x105d48480, 0x106466d90})
        /opt/homebrew/Cellar/go/1.18.1/libexec/src/runtime/panic.go:838 +0x204
github.com/etclabscore/go-openrpc-reflect.getAstFuncDecl({0x105e2d4a0?, 0x14000492000?, 0x17?}, {{0x105ca819b, 0x17}, {0x0, 0x0}, {0x105e7d758, 0x1400010f980}, {0x1400010f980, ...}, ...})
        /Users/ziogaschr/Sites/go/pkg/mod/github.com/etclabscore/go-openrpc-reflect@v0.0.36/common.go:372 +0x31c
github.com/etclabscore/go-openrpc-reflect.receiverMethods({0x105e7cf88, 0x1400048ed00}, {0x105223d49, 0x5}, {0x105e2d4a0?, 0x14000492000?})
        /Users/ziogaschr/Sites/go/pkg/mod/github.com/etclabscore/go-openrpc-reflect@v0.0.36/common.go:74 +0x2c4
github.com/etclabscore/go-openrpc-reflect.(*EthereumReflectorT).ReceiverMethods(0x105e2eea0?, {0x105223d49?, 0x1400026a200?}, {0x105e2d4a0?, 0x14000492000?})
        /Users/ziogaschr/Sites/go/pkg/mod/github.com/etclabscore/go-openrpc-reflect@v0.0.36/go-ethereum.go:22 +0x74
github.com/etclabscore/go-openrpc-reflect.(*Document).Discover(0x140006227e0)
        /Users/ziogaschr/Sites/go/pkg/mod/github.com/etclabscore/go-openrpc-reflect@v0.0.36/document.go:188 +0x2f8
github.com/ethereum/go-ethereum/node.(*RPCDiscoveryService).Discover(0x2?)
        /Users/ziogaschr/Sites/go/src/github.com/etclabscore/core-geth/node/openrpc.go:38 +0x24
reflect.Value.call({0x140002d41e0?, 0x14000011ee0?, 0x1067445b8?}, {0x1052227ea, 0x4}, {0x140009641e0, 0x1, 0x104ce143c?})
        /opt/homebrew/Cellar/go/1.18.1/libexec/src/reflect/value.go:556 +0x5e4
reflect.Value.Call({0x140002d41e0?, 0x14000011ee0?, 0x1400094fb80?}, {0x140009641e0, 0x1, 0x2})
        /opt/homebrew/Cellar/go/1.18.1/libexec/src/reflect/value.go:339 +0x98
github.com/ethereum/go-ethereum/rpc.(*callback).call(0x1400091ed20, {0x105e77af0?, 0x14000f21600}, {0x14000425a80, 0xc}, {0x0, 0x0, 0x104cdb460?})
        /Users/ziogaschr/Sites/go/src/github.com/etclabscore/core-geth/rpc/service.go:205 +0x38c
github.com/ethereum/go-ethereum/rpc.(*handler).runMethod(0x0?, {0x105e77af0?, 0x14000f21600?}, 0x14000622af0, 0x0?, {0x0?, 0x100010000?, 0x10d75fb70?})
        /Users/ziogaschr/Sites/go/src/github.com/etclabscore/core-geth/rpc/handler.go:389 +0x44
github.com/ethereum/go-ethereum/rpc.(*handler).handleCall(0x140006f1170, 0x14000964180, 0x14000622af0)
        /Users/ziogaschr/Sites/go/src/github.com/etclabscore/core-geth/rpc/handler.go:337 +0x1dc
github.com/ethereum/go-ethereum/rpc.(*handler).handleCallMsg(0x140006f1170, 0x14000964180?, 0x14000622af0)
        /Users/ziogaschr/Sites/go/src/github.com/etclabscore/core-geth/rpc/handler.go:298 +0x80
github.com/ethereum/go-ethereum/rpc.(*handler).handleMsg.func1(0x14000964180)
        /Users/ziogaschr/Sites/go/src/github.com/etclabscore/core-geth/rpc/handler.go:139 +0x38
github.com/ethereum/go-ethereum/rpc.(*handler).startCallProc.func1()
        /Users/ziogaschr/Sites/go/src/github.com/etclabscore/core-geth/rpc/handler.go:226 +0xc4
created by github.com/ethereum/go-ethereum/rpc.(*handler).startCallProc
        /Users/ziogaschr/Sites/go/src/github.com/etclabscore/core-geth/rpc/handler.go:222 +0x90
 
WARN [08-23|14:31:19.397] Served rpc.discover                      reqid=1 duration=17.6825ms err="method handler crashed"
INFO [08-23|14:31:19.397] Ethereum protocol stopped 
INFO [08-23|14:31:19.397] Transaction pool stopped 
INFO [08-23|14:31:19.397] Writing cached state to disk             block=2 hash=4bab76..d2d838 root=0867e4..7f573b
INFO [08-23|14:31:19.397] Persisted trie from memory database      nodes=4 size=576.00B time="9.834µs"  gcnodes=0 gcsize=0.00B gctime=0s livenodes=4  livesize=406.00B
INFO [08-23|14:31:19.397] Writing cached state to disk             block=1 hash=82b641..3dc6ab root=08c303..e26e42
INFO [08-23|14:31:19.397] Persisted trie from memory database      nodes=3 size=406.00B time="2.833µs"  gcnodes=0 gcsize=0.00B gctime=0s livenodes=1  livesize=0.00B
INFO [08-23|14:31:19.397] Blockchain stopped