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.

STD_TEST.st
STD_RESSOURCE.c
LOCATED_VARIABLES.h
POUS.c
test
STD_CONF.c
SFC_TEST.st
test.exe
plc.st
POUS.h
VARIABLES.csv