linter segfault when clojure.core/list is excluded in a namespace containing a macro

[benalbrecht]

joker crashes when running joker --lint against the following clojure source file:

(ns foo
  (:refer-clojure :exclude [list]))

(defmacro bar [baz]
  `(identity ~baz))

stack trace:

$ joker --lint foo.clj 
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
        panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x74190d]

goroutine 1 [running]:
github.com/candid82/joker/core.TryParse.func1(0xc00056bb18)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1863 +0x16b
panic(0x923600, 0xe58640)
        /usr/local/Cellar/go/1.14/libexec/src/runtime/panic.go:967 +0x15d
github.com/candid82/joker/core.parseSymbol(0xb0ae60, 0xc0001d95f0, 0xc00056bbb8, 0x0, 0x0)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1808 +0x4cd
github.com/candid82/joker/core.Parse(0xb0ae60, 0xc0001d95f0, 0xc00056bbb8, 0xb0d200, 0xc000438980)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1834 +0x3f7
github.com/candid82/joker/core.parseList(0xb0a260, 0xc000438980, 0xc00056bbb8, 0x0, 0x0)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1643 +0x336
github.com/candid82/joker/core.Parse(0xb0a260, 0xc000438980, 0xc00056bbb8, 0x129aba0, 0xe52b00)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1832 +0x524
github.com/candid82/joker/core.parseSeq(0xb0d200, 0xc000438b00, 0xc00056bbb8, 0x0, 0x0, 0xc000567210)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:625 +0xfa
github.com/candid82/joker/core.parseList(0xb0a260, 0xc000438b40, 0xc00056bbb8, 0x0, 0x0)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1664 +0x5de
github.com/candid82/joker/core.Parse(0xb0a260, 0xc000438b40, 0xc00056bbb8, 0x129aba0, 0xe56a00)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1832 +0x524
github.com/candid82/joker/core.parseSeq(0xb0d200, 0xc000438bc0, 0xc00056bbb8, 0x0, 0x0, 0xc000567a78)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:625 +0xfa
github.com/candid82/joker/core.parseList(0xb0a260, 0xc000438e00, 0xc00056bbb8, 0x0, 0x0)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1664 +0x5de
github.com/candid82/joker/core.Parse(0xb0a260, 0xc000438e00, 0xc00056bbb8, 0x129aba0, 0x7f1378978358)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1832 +0x524
github.com/candid82/joker/core.parseBody(0xb0d200, 0xc000438fc0, 0xc00056bbb8, 0x0, 0x0, 0x0)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:777 +0x14a
github.com/candid82/joker/core.addArity(0xc0004d8a80, 0xb0d200, 0xc0004392c0, 0xc00056bbb8)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:856 +0x2af
github.com/candid82/joker/core.parseFn(0xb0a260, 0xc0004395c0, 0xc00056bbb8, 0x0, 0x0)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:947 +0x483
github.com/candid82/joker/core.parseList(0xb0a260, 0xc0004395c0, 0xc00056bbb8, 0x0, 0x0)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1571 +0x2641
github.com/candid82/joker/core.Parse(0xb0a260, 0xc0004395c0, 0xc00056bbb8, 0xb0a200, 0xc0004395c0)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1832 +0x524
github.com/candid82/joker/core.parseList(0xb0a260, 0xc000513600, 0xc00056bbb8, 0x0, 0x0)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1539 +0xbe
github.com/candid82/joker/core.Parse(0xb0a260, 0xc000513600, 0xc00056bbb8, 0xc000513600, 0x0)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1832 +0x524
github.com/candid82/joker/core.parseDef(0xb0a260, 0xc000513a80, 0xc00056bbb8, 0xb0d200, 0xc000513a80)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:734 +0x807
github.com/candid82/joker/core.parseList(0xb0a260, 0xc000513a80, 0xc00056bbb8, 0x0, 0x0)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1587 +0x2415
github.com/candid82/joker/core.Parse(0xb0a260, 0xc000513a80, 0xc00056bbb8, 0xb0a200, 0xc000513a80)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1832 +0x524
github.com/candid82/joker/core.parseList(0xb0a260, 0xc000512300, 0xc00056bbb8, 0x0, 0x0)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1539 +0xbe
github.com/candid82/joker/core.Parse(0xb0a260, 0xc000512300, 0xc00056bbb8, 0x129aba0, 0x0)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1832 +0x524
github.com/candid82/joker/core.parseBody(0xb0d200, 0xc0005124c0, 0xc00056bbb8, 0x0, 0x0, 0x0)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:777 +0x14a
github.com/candid82/joker/core.parseList(0xb0a260, 0xc000512500, 0xc00056bbb8, 0x0, 0x0)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1620 +0x18fc
github.com/candid82/joker/core.Parse(0xb0a260, 0xc000512500, 0xc00056bbb8, 0xb0a200, 0xc000512500)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1832 +0x524
github.com/candid82/joker/core.parseList(0xb0a260, 0xc0000d0f00, 0xc00056bbb8, 0x0, 0x0)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1539 +0xbe
github.com/candid82/joker/core.Parse(0xb0a260, 0xc0000d0f00, 0xc00056bbb8, 0xb08aa0, 0xc000435f40)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1832 +0x524
github.com/candid82/joker/core.TryParse(0xb0a260, 0xc0000d0f00, 0xc00056bbb8, 0x0, 0x0, 0x0, 0x0)
        /Users/candid/go/src/github.com/candid82/joker/core/parse.go:1867 +0x78
github.com/candid82/joker/core.ProcessReader(0xc000554be0, 0x7ffd25b601e4, 0x7, 0x2, 0x0, 0x0)
        /Users/candid/go/src/github.com/candid82/joker/core/procs.go:1745 +0x30d
main.processFile(0x7ffd25b601e4, 0x7, 0x2, 0x0, 0x0)
        /Users/candid/go/src/github.com/candid82/joker/main.go:113 +0x1eb
main.lintFile(0x7ffd25b601e4, 0x7, 0x0, 0x0, 0x0)
        /Users/candid/go/src/github.com/candid82/joker/main.go:277 +0xb7
main.main()
        /Users/candid/go/src/github.com/candid82/joker/main.go:834 +0x1181