segfault when a undefined name is accessed

[tanmaykm]

I see a segfault in the REPL when a undefined name is referenced.

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  | | |_| | | | (_| |  |  Version 0.5.0-pre+5609 (2016-07-22 07:00 UTC)
 _/ |\__'_|_|_|\__'_|  |  Commit 21f28c9* (0 days old master)
|__/                   |  x86_64-linux-gnu

julia> versioninfo()
Julia Version 0.5.0-pre+5609
Commit 21f28c9* (2016-07-22 07:00 UTC)
Platform Info:
  System: Linux (x86_64-linux-gnu)
  CPU: Intel(R) Core(TM) i7-4700MQ CPU @ 2.40GHz
  WORD_SIZE: 64
  BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Haswell)
  LAPACK: libopenblas64_
  LIBM: libopenlibm
  LLVM: libLLVM-3.7.1 (ORCJIT, haswell)

julia> x

signal (11): Segmentation fault
while loading no file, in expression starting on line 0
jl_f_tuple at /data/Work/julia/sources/julia/src/builtins.c:648
eval_user_input at ./REPL.jl:74
jl_call_method_internal at /data/Work/julia/sources/julia/src/julia_internal.h:177 [inlined]
jl_apply_generic at /data/Work/julia/sources/julia/src/gf.c:2034
macro expansion at ./REPL.jl:92 [inlined]
#3 at ./event.jl:46
jl_call_method_internal at /data/Work/julia/sources/julia/src/julia_internal.h:177 [inlined]
jl_apply_generic at /data/Work/julia/sources/julia/src/gf.c:2034
jl_apply at /data/Work/julia/sources/julia/src/julia.h:1394 [inlined]
start_task at /data/Work/julia/sources/julia/src/task.c:253
unknown function (ip: 0xffffffffffffffff)
Allocations: 4495927 (Pool: 4494783; Big: 1144); GC: 6
Segmentation fault

This works fine:

$ julia -e 'x'
ERROR: UndefVarError: x not defined
 in eval(::Module, ::Any) at ./boot.jl:234
 in process_options(::Base.JLOptions) at ./client.jl:239
 in _start() at ./client.jl:318

[tkelman]

#17288 #17548