Crash in ary_concat()

The code above raises a segmentation fault both in mruby and mruby-engine ``` N *case when nil ->()do end def e()end end# ```` ASAN report : ``` line 1:3: '*' interpreted as argument prefix ASAN:SIGSEGV ================================================================= ==111090==ERROR: AddressSanitizer: SEGV on unknown address 0x0000000c (pc 0x08449c8e sp 0xfffd4e20 bp 0x0000000c T0) #0 0x8449c8d in ary_concat /root/fuzzing/mruby/src/array.c:260 #1 0x8449c8d in mrb_ary_concat /root/fuzzing/mruby/src/array.c:279 #2 0x850bfe1 in mrb_vm_exec /root/fuzzing/mruby/src/vm.c:2288 #3 0x852f901 in mrb_vm_run /root/fuzzing/mruby/src/vm.c:823 #4 0x852f901 in mrb_top_run /root/fuzzing/mruby/src/vm.c:2614 #5 0x82e3a4b in mrb_load_exec /root/fuzzing/mruby/mrbgems/mruby-compiler/core/parse.y:5760 #6 0x82e6b9b in mrb_load_nstring_cxt /root/fuzzing/mruby/mrbgems/mruby-compiler/core/parse.y:5782 #7 0x82e6b9b in mrb_load_string_cxt /root/fuzzing/mruby/mrbgems/mruby-compiler/core/parse.y:5794 #8 0x82e6dc4 in mrb_load_string /root/fuzzing/mruby/mrbgems/mruby-compiler/core/parse.y:5800 #9 0x80d22e8 in main /root/fuzzing/mruby/bin/fuzz.c:13 #10 0xf74e5636 in __libc_start_main (/lib/i386-linux-gnu/libc.so.6+0x18636) #11 0x80d1fc4 in _start (/home/simo/test/news/xx/bin/zz+0x80d1fc4) ``` Sandbox crash report : ``` home/simo/mruby-engine-normal/bin/sandbox:20: [BUG] Segmentation fault at 0x00000000000018 ruby 2.3.1p112 (2016-04-26) [x86_64-linux-gnu] -- Control frame information ----------------------------------------------- c:0003 p:---- s:0010 e:000009 CFUNC :sandbox_eval c:0002 p:0201 s:0005 E:0009d8 EVAL /home/simo/mruby-engine-normal/bin/sandbox:20 [FINISH] c:0001 p:0000 s:0002 E:002180 (none) [FINISH] -- Ruby level backtrace information ---------------------------------------- /home/simo/mruby-engine-normal/bin/sandbox:20:in `<main>' /home/simo/mruby-engine-normal/bin/sandbox:20:in `sandbox_eval' -- Machine register context ------------------------------------------------ RIP: 0x00007f2932c2aa7e RBP: 0x00007f29317b8a00 RSP: 0x00007f29317aaac0 RAX: 0x1fffffffffffffff RBX: 0x00007f29317ac4e0 RCX: 0x0000000000000003 RDX: 0x00007f29317b40d0 RDI: 0x00007f29317ac4e0 RSI: 0x0000000000000000 R8: 0x0000000000000010 R9: 0x0000000000000000 R10: 0x000000000000001f R11: 0x00007f29317bb520 R12: 0x0000000000000000 R13: 0x00007f29317ac4e0 R14: 0x00007f29317ac4e0 R15: 0x0000000001810038 EFL: 0x0000000000010206 ``` Thanks