fix some functoins if optional parameters are omitted

[ingoj]

in some functions, $user and $types should be optional parameters. in ILIAS 8 (and posibly 9/trunk) these parameters must be supplied, but the function itself contains checks for these paramaters. This PR contains a possible, but untested fix.

[ingoj]

Mantis ID: 41487

[jeph864]

@ingoj, Can you add the parameter signatures to inc.soap_functions.php? Without such adjustments there would be a type error

[ingoj]

@jeph864, I updated inc.soap_functions.php accordingly, I hope everything is fine now. Sorry I could not test the changes.

[jeph864]

@ingoj , thanks for the PR