Comment 1 for bug 1028026

It seems like there are some type error that causes debugger run into a loop.
After --disable-debugger I got the following error messages and backtrace.

* unhandled TYPE-ERROR in thread #<SB-THREAD:THREAD "main thread" RUNNING
                                  {1002971023}>:
  The value -1960034 is not of type UNSIGNED-BYTE.

0: (SB-DEBUG::MAP-BACKTRACE
    #<CLOSURE (LAMBDA # :IN BACKTRACE) {1003E21DDB}>
    :START
    0
    :COUNT
    128)
1: (BACKTRACE 128 #<SYNONYM-STREAM :SYMBOL SB-SYS:*STDERR* {1000169AE3}>)
2: (SB-DEBUG::DEBUGGER-DISABLED-HOOK
    #<TYPE-ERROR expected-type: UNSIGNED-BYTE datum: -1960034>
    #<unavailable argument>)
3: (SB-DEBUG::RUN-HOOK
    *INVOKE-DEBUGGER-HOOK*
    #<TYPE-ERROR expected-type: UNSIGNED-BYTE datum: -1960034>)
4: (INVOKE-DEBUGGER #<TYPE-ERROR expected-type: UNSIGNED-BYTE datum: -1960034>)
5: (ERROR TYPE-ERROR :DATUM -1960034 :EXPECTED-TYPE UNSIGNED-BYTE)
6: (SB-KERNEL::OBJECT-NOT-TYPE-ERROR-HANDLER
    #<unavailable argument>
    #.(SB-SYS:INT-SAP #X7FFFF6CDF1A0)
    #<SB-ALIEN-INTERNALS:ALIEN-VALUE :SAP #X7FFFF6CDEB80 :TYPE (*
                                                                (STRUCT
                                                                 SB-VM::OS-CONTEXT-T-STRUCT))>
    (84 21))
7: (SB-KERNEL:INTERNAL-ERROR
    #.(SB-SYS:INT-SAP #X7FFFF6CDEB80)
    #<unavailable argument>)
8: ("foreign function: call_into_lisp")
9: ("foreign function: funcall2")
10: ("foreign function: interrupt_internal_error")
11: ("foreign function: handle_trap")
12: ("foreign function: #x412C33")
13: (GET-INTERNAL-REAL-TIME)
14: (SB-SYS:DECODE-TIMEOUT NIL)
15: (SB-SYS:WAIT-UNTIL-FD-USABLE 0 :INPUT NIL T)
16: (SB-IMPL::REFILL-INPUT-BUFFER
     #<SB-SYS:FD-STREAM for "standard input" {10029713B3}>)
17: (SB-IMPL::INPUT-CHAR/UTF-8
     #<SB-SYS:FD-STREAM for "standard input" {10029713B3}>
     NIL
     #:EOF-OBJECT)
18: ((LAMBDA (&REST REST) :IN SB-IMPL::GET-EXTERNAL-FORMAT)
     #<SB-SYS:FD-STREAM for "standard input" {10029713B3}>
     NIL
     #:EOF-OBJECT)
19: (READ-CHAR
     #<SB-SYS:FD-STREAM for "standard input" {10029713B3}>
     NIL
     #:EOF-OBJECT
     #<unused argument>)
20: (READ-CHAR
     #<SYNONYM-STREAM :SYMBOL SB-SYS:*STDIN* {10001B3173}>
     NIL
     #:EOF-OBJECT
     #<unused argument>)
21: (SB-IMPL::%READ-PRESERVING-WHITESPACE
     #<SYNONYM-STREAM :SYMBOL SB-SYS:*STDIN* {10001B3173}>
     NIL
     (NIL)
     T)
22: (SB-IMPL::%READ-PRESERVING-WHITESPACE
     #<SYNONYM-STREAM :SYMBOL SB-SYS:*STDIN* {10001B3173}>
     NIL
     (NIL)
     NIL)
23: (READ #<SYNONYM-STREAM :SYMBOL SB-SYS:*STDIN* {10001B3173}> NIL (NIL) NIL)
24: (SB-IMPL::REPL-READ-FORM-FUN
     #<SYNONYM-STREAM :SYMBOL SB-SYS:*STDIN* {10001B3173}>
     #<unavailable argument>)
25: (SB-IMPL::REPL-FUN NIL)
26: ((LAMBDA () :IN SB-IMPL::TOPLEVEL-REPL))
27: (SB-IMPL::%WITH-REBOUND-IO-SYNTAX
     #<CLOSURE (LAMBDA # :IN SB-IMPL::TOPLEVEL-REPL) {1003E1248B}>)
28: (SB-IMPL::TOPLEVEL-REPL NIL)
29: (SB-IMPL::TOPLEVEL-INIT)
30: ((FLET #:WITHOUT-INTERRUPTS-BODY-237819 :IN SAVE-LISP-AND-DIE))
31: ((LABELS SB-IMPL::RESTART-LISP :IN SAVE-LISP-AND-DIE))

unhandled condition in --disable-debugger mode, quitting