BMessage::ReplaceData() shouldn't care about fixed size if there is no array

[axeld]

The "fixedSize" argument should only be taken into account for arrays - and not for the non-array variant of AddData(). Test application is attached, expected output would be: "gurkensalat"; currently, only "gurke" is seen :-)

[mmlr]

Actually allowing this is a Dano behavior. Under R5 your test application behaves like under Haiku and returns B_BAD_VALUE on ReplaceData() resulting in "gurke" at the end.

As AddData() has the default value of true for it's fixedSize argument, it only makes sense to set the fixedSize flag for the field and then enforce it. If you want non fixed size data, you obviously would set fixedSize to false on AddData().

If you don't object I'd like to close this bug as invalid.

[axeld]

While I think the Dano behaviour is cleaner (because there is no array I would care about), I'm fine with closing the bug as invalid, since it duplicates R5 :) Thanks for checking.