Segmentation fault - mrb_gc_mark

``` # gdb /root/mruby-engine/ext/mruby_engine/mruby/bin/mirb GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.04) 7.11.1 Copyright (C) 2016 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "x86_64-linux-gnu". Type "show configuration" for configuration details. For bug reporting instructions, please see: <http://www.gnu.org/software/gdb/bugs/>. Find the GDB manual and other documentation resources online at: <http://www.gnu.org/software/gdb/documentation/>. For help, type "help". Type "apropos word" to search for commands related to "word"... Reading symbols from /root/mruby-engine/ext/mruby_engine/mruby/bin/mirb...done. (gdb) run 3.rb Starting program: /root/mruby-engine/ext/mruby_engine/mruby/bin/mirb 3.rb mirb - Embeddable Interactive Ruby Shell => [300000, 8] line 2: syntax error, unexpected tIDENTIFIER, expecting keyword_do or '{' or '(' line 3: syntax error, unexpected tAMPER Program received signal SIGSEGV, Segmentation fault. mrb_gc_mark (mrb=0x6cf010, obj=0x305c3030325c3737) at /root/mruby-engine/ext/mruby_engine/mruby/src/gc.c:696 696 if (!is_white(obj)) return; (gdb) x/1i $rip => 0x410f75 <mrb_gc_mark+5>: movzbl 0x1(%rsi),%eax (gdb) list *$rip 0x410f75 is in mrb_gc_mark (/root/mruby-engine/ext/mruby_engine/mruby/src/gc.c:696). 691 692 MRB_API void 693 mrb_gc_mark(mrb_state *mrb, struct RBasic *obj) 694 { 695 if (obj == 0) return; 696 if (!is_white(obj)) return; 697 mrb_assert((obj)->tt != MRB_TT_FREE); 698 add_gray_list(mrb, &mrb->gc, obj); 699 } 700 (gdb) bt ```