When doing ```gpac -h bench``` for #2682, I got this output:
```
-bench: check decoding speed of source. Syntax: `gpac -bench source.mp4`
session error: Filter not found for the desired type
```

I don't think we should return an error in this case. Is there a good reason to do so?

For the record the error comes from:
```
		if (print_filters(argc, argv, argmode)==GF_FALSE)
			e = GF_FILTER_NOT_FOUND
```
Error returned while using -h
This is a GitHub Issue
repo:gpac
owner:gpac
Title : Error returned while using -h
Issue date:

--- start body ---
When doing ```gpac -h bench``` for #2682, I got this output:
```
-bench: check decoding speed of source. Syntax: `gpac -bench source.mp4`
session error: Filter not found for the desired type
```

I don't think we should return an error in this case. Is there a good reason to do so?

For the record the error comes from:
```
		if (print_filters(argc, argv, argmode)==GF_FALSE)
			e = GF_FILTER_NOT_FOUND
```
--- end body ---
