Core dump in really_free_array

Imported from http://bugzilla.roxen.com/bugzilla/show_bug.cgi?id=5509

Reported by Marcus Wellhardh wellhard@roxen.com

Roxen crashed and restarted with this error (roxen-4.5.410-release-ep-macosx_x86.sh)

    Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
    Exception Codes: KERN_INVALID_ADDRESS at 0x00000000c1f0cd87
    Crashed Thread:  0
    
    Thread 0 Crashed:
    0  0x0003ec9b really_free_array + 59 (array.c:125)
    1  0x00047642 backend_do_call_outs + 290 (backend.cmod:1970)
    2  0x00048581 low_backend_once + 993 (backend.cmod:1444)
    3  0x00048a60 f_Backend_cq__backtick_28_29 + 112 (backend.cmod:1484)
    4  0x00015855 low_mega_apply + 3109 (apply_low.h:195)
    5  0x000178a2 opcode_F_APPLY_AND_POP + 98 (interpret_functions.h:1878)
    6  0x010b37cb 0 + 17512395
    7  0x00017ee8 o_catch + 232 (interpret.c:1831)
    8  0x00017f9d opcode_F_CATCH + 61 (interpret_functions.h:1195)
    9  0x010b377d 0 + 17512317
    10 0x00016235 mega_apply + 101 (interpret.c:1787)
    11 0x00018bf7 apply + 55 (interpret.c:2095)
    12 0x00083f93 main + 2579 (main.c:757)
    13 0x00001eb2 _start + 216
    14 0x00001dd9 start + 41