[Bug-apl] Segmentation fault on out of bounds indexing

[Kacper Gutowski]

Indexing array of rank > 1 with index < ⎕IO results 
in segmentation fault instead of index error.

      ⎕IO
1
      (1 1⍴0)[0;]


====================================================
SEGMENTATION FAULT

----------------------------------------
-- Stack trace at main.cc:111
----------------------------------------
0x7f8f94312995 __libc_start_main
0x433e5d  main
0x5114fd   Workspace::immediate_execution(bool)
0x45edfd    Command::process_line()
0x45dd9b     Command::process_line(UCS_string&)
0x466378      Executable::execute_body() const
0x4d35b0       StateIndicator::run()
0x484fba        Prefix::reduce_statements()
0x4823b1         Prefix::reduce_A_C__()
0x50f144          Value::index(Token&) const
0x50b195           Value::index(IndexExpr const&) const
0x456b7b            Cell::init(Cell const&)
0x7f8f95e09210             
0x472d1a              
========================================
====================================================


-k