Do not crash when checking semantics of undeclared symbolic_variable.
NOTE: this update may have broken the printing of error messages
during semantic analysis of IL code.
FUNCTION WEIGH : WORD (* BCD encoded *)
VAR_INPUT (* "EN" input is used to indicate "scale ready" *)
weigh_command : BOOL;
gross_weight : WORD ; (* BCD encoded *)
tare_weight : INT ;
END_VAR
(* Function Body *)
IF weigh_command THEN
WEIGH := INT_TO_BCD (BCD_TO_INT(gross_weight) - tare_weight);
END_IF ;
END_FUNCTION (* Implicit "ENO" *)