find symbols in proper scope when debugging (bug #40397) * lex.h (lexical_feedback::symbol_table_context::init_scope): Delete member variable and all uses. (lexical_feedback::symbol_table_context::pop): Assert that the context is not empty before popping. (lexical_feedback::symbol_table_context::push): Use default argument. (lexical_feedback::symbol_table_context::curr_scope): If empty, return symbol_table::current_scope, not the initial scope in effect when the object is created. * oct-parse.in.yy (octave_base_parser::make_anon_fcn_handle, octave_base_parser::recover_from_parsing_function): Don't check for empty lexer.symtab_context here.