need help in simatic s7 300

Hi Everybody! I had just uploaded one of our machine program.
PLC: s7-300, using simatic s7 v5.4.

In the program I had read this OB's

OB80- CYCLE TIME FAULT
OB82- I/O POINT FAULT
OB86-LOSS RACK FAULT
OB121- PROGRAMMING ERROR
OB122- MODULE ACCES ERROR

I'de open all those OB's but i found no program inside, no STL,FBD and even LDR. i had only read "cycle time fault" for OB80 and so on. I've wonder why they exist in program, in fact they were all empty.
Can somebody please tell me why?
Thank you in advance, I really appreciate for your help...

They are there to keep the CPU in run mode in case of a fault (Profibus and watchdog)

If the OB is not present, the PLC will stop when a related fault occurs.

The idea being, once programmed the user can record the error has happened and store the fault cause and a decision can be made on whether to stop the PLC with the STOP SFB.

In reality, many programmers leave them in blank so they never stop.

I'd be wary of keeping scan time error and programming error in.

If you are doing program modifications on a running plant, then it may be better to leave OB121 in. You wont stop the whole plant then due to a trivial programming error or typo.
Of course it depends on if an error can have critical consequences for the machine or plant if left running (in that case maybe online programming should be avoided !).

I think that it is unprofessional to have a completely blank error OBs. As a minimum, an error OB should trigger a HMI alarm message.