Assertion failed: 0 && "Cell::init_other() called on base class"

[Ben Harris]

I've caused an assertion failure in svn 1297.  The expression is wrong (I 
didn't need to use ¨ at all), but it shouldn't cause an assertion failure:

      ⊂('\"')⍳¨'b\c'

==============================================================================
Assertion failed: 0 && "Cell::init_other() called on base class"
in Function:      init_other
in file:          Cell.hh:67

Call stack:

----------------------------------------
-- Stack trace at Cell.hh:67
----------------------------------------
0xF786CE81 __libc_start_main
0x565CB5A8  main
0x567985C7   Workspace::immediate_execution(bool)
0x5663EAFE    Command::process_line()
0x5663F6A9     Command::do_APL_expression(UCS_string&)
0x5663EBEE      Command::finish_context()
0x56648636       Executable::execute_body() const
0x567281F1        StateIndicator::run()
0x56686039         Prefix::reduce_statements()
0x5667D964          Prefix::reduce_A_F_B_()
0x56651301           DerivedFunction::eval_AB(Value_P, Value_P)
0x5660899A            Bif_OPER1_EACH::eval_ALB(Value_P, Token&, Value_P)
0x5662058E             Cell::to_value(char const*) const
0x56621ECB
0x565E3F6F               do_Assert(char const*, char const*, char const*, int)
========================================

SI stack:

Depth:      0
Exec:       0x57737a70
Safe exec:  0
Pmode:      ◊  ⊂('\"')⍳¨'b\c'
PC:         4 (7) ⊂
Stat:       ⊂('\"')⍳¨'b\c'
err_code:   0x0


==============================================================================

--
Ben Harris