PIL.Image does not work

I tried loading an image using PIL and it crashed julia. Crashes for different images too. Here is what I ran:

```
using PyCall
@pyimport PIL.Image as Image
im = Image.open("examples/1.jpg")
```

The following is the error message:
```
signal (11): Segmentation fault
while loading no file, in expression starting on line 0
unknown function (ip: 0x7fa37267cbcf)
pyarray_dims at /home/vipin/opt/julia/packages/v0.6/PyCall/src/conversions.jl:360
py2array at /home/vipin/opt/julia/packages/v0.6/PyCall/src/conversions.jl:380
unknown function (ip: 0x7fa37a8eed26)
jl_call_fptr_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:339 [inlined]
jl_call_method_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:358 [inlined]
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:1926
jl_apply at /buildworker/worker/package_linux64/build/src/julia.h:1424 [inlined]
jl_invoke at /buildworker/worker/package_linux64/build/src/gf.c:51
convert at /home/vipin/opt/julia/packages/v0.6/PyCall/src/numpy.jl:463
unknown function (ip: 0x7fa37a8ecee6)
jl_call_fptr_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:339 [inlined]
jl_call_method_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:358 [inlined]
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:1926
convert at /home/vipin/opt/julia/packages/v0.6/PyCall/src/conversions.jl:808
#pycall#71 at /home/vipin/opt/julia/packages/v0.6/PyCall/src/PyCall.jl:675
jl_call_fptr_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:339 [inlined]
jl_call_method_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:358 [inlined]
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:1926
jl_apply at /buildworker/worker/package_linux64/build/src/julia.h:1424 [inlined]
jl_f__apply at /buildworker/worker/package_linux64/build/src/builtins.c:426
pycall at /home/vipin/opt/julia/packages/v0.6/PyCall/src/PyCall.jl:675
jl_call_fptr_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:339 [inlined]
jl_call_method_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:358 [inlined]
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:1926
jl_apply at /buildworker/worker/package_linux64/build/src/julia.h:1424 [inlined]
jl_f__apply at /buildworker/worker/package_linux64/build/src/builtins.c:426
#call#72 at /home/vipin/opt/julia/packages/v0.6/PyCall/src/PyCall.jl:678
jl_call_fptr_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:339 [inlined]
jl_call_method_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:358 [inlined]
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:1926
jl_apply at /buildworker/worker/package_linux64/build/src/julia.h:1424 [inlined]
jl_f__apply at /buildworker/worker/package_linux64/build/src/builtins.c:426
PyObject at /home/vipin/opt/julia/packages/v0.6/PyCall/src/PyCall.jl:678
jl_call_fptr_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:339 [inlined]
jl_call_method_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:358 [inlined]
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:1926
do_call at /buildworker/worker/package_linux64/build/src/interpreter.c:75
eval at /buildworker/worker/package_linux64/build/src/interpreter.c:242
eval_body at /buildworker/worker/package_linux64/build/src/interpreter.c:543
jl_interpret_toplevel_thunk at /buildworker/worker/package_linux64/build/src/interpreter.c:692
jl_toplevel_eval_flex at /buildworker/worker/package_linux64/build/src/toplevel.c:592
jl_toplevel_eval_in at /buildworker/worker/package_linux64/build/src/builtins.c:496
eval at ./boot.jl:235
unknown function (ip: 0x7fa3990dad2f)
jl_call_fptr_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:339 [inlined]
jl_call_method_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:358 [inlined]
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:1926
eval_user_input at ./REPL.jl:66
unknown function (ip: 0x7fa39915c18f)
jl_call_fptr_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:339 [inlined]
jl_call_method_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:358 [inlined]
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:1926
macro expansion at ./REPL.jl:97 [inlined]
#1 at ./event.jl:73
unknown function (ip: 0x7fa37a89434f)
jl_call_fptr_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:339 [inlined]
jl_call_method_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:358 [inlined]
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:1926
jl_apply at /buildworker/worker/package_linux64/build/src/julia.h:1424 [inlined]
start_task at /buildworker/worker/package_linux64/build/src/task.c:267
unknown function (ip: 0xffffffffffffffff)
Allocations: 5810962 (Pool: 5809315; Big: 1647); GC: 11
Segmentation fault (core dumped)
```

This is the julia version I am running (it's the generic linux binary from the website): `Version 0.6.2 (2017-12-13 18:08 UTC) x86_64-pc-linux-gnu`

This is the python version: `Python 2.7.12`. It's the default install on ubuntu 16.04.

Reproduce the provided Julia 0.6.2 and Python 2.7.12 snippet with PyCall and PIL.Image.open. Start by reading src/conversions.jl, src/numpy.jl, and src/PyCall.jl at the stack-trace locations, then determine why the image load reaches a segmentation fault; done means the same image-loading example no longer crashes Julia.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.