parse error due to redundant paranthesis

[Rajashekar R M]

I am crashing the program when using redundant paranthesis to create arrays
```
      y ← 1 ((2))

==============================================================================
Assertion failed: !sub_val->is_simple_scalar()
in Function:      PointerCell
in file:          PointerCell.cc:30

Call stack:

----------------------------------------
-- Stack trace at PointerCell.cc:30
----------------------------------------
0x7F7F24566B25 __libc_start_main
0x556355C13C16  main
0x556355D6C816   Workspace::immediate_execution(bool)
0x556355C667B7    Command::process_line()
0x556355C67275     Command::do_APL_expression(UCS_string&)
0x556355C73728      StatementList::fix(UCS_string const&, char const*)
0x556355C7316C       Executable::parse_body_line(Function_Line, UCS_string 
const&, bool, bool, char const*, bool)
0x556355C9D74A        Parser::parse(UCS_string const&, Token_string&) const
0x556355C9D3CB         Parser::parse(Token_string const&, Token_string&) const
0x556355C9D14C          Parser::parse_statement(Token_string&)
0x556355C9C941           Parser::collect_constants(Token_string&)
0x556355C9C64E            Parser::create_vector_value(Token_string&, int, int)
0x556355CA779E             PointerCell::PointerCell(Value*, Value&)
0x556355C2A878              do_Assert(char const*, char const*, char const*, 
int)
========================================

SI stack:


==============================================================================
*** Command::process_line() caught other exception ***

Goodbye.
Session duration: 39.844 seconds 

Process apl finished
```

This is not happenning for a single pair y ← 1 (2)