ovf player should allow blank labels

[joereddington]

Generated aids show a '04' below the 'clear' button in the bottom left corner of the top page.

This is because the grid.py class adds a label to any button that doesn't have one (in this case, the clear button is entirely described by the icon) when exporting to obf format. This is needed because ovfplayer requires one.

Next comment talks about if ovfplayer should require one.

In practice - I changed the CK20 pageset so the error no longer appears by default, but we should probably fix in case a user does a thing in future.

[joereddington]

I can remove the label from the obf file, but I get this error from ovfplayer:

Now, I should check to see if this is the same criteria as the main obf site uses.

I used the validator here - it produced this set of errors (because I gave it the obf file without the linked images)

I then put it through the previewer on the same site and got this:

The images are obviously missing - but it does seem to accept the lack of a label.

This does start to look like it's something that has to be changed at the player level, but I have a horrible feeling that there's a screenshot coming my way of me saying something like "buttons have to have labels".

[joereddington]

I've updated the Communicate pageset so the error doesn't occur (and updated the demo and link on the OVF site) - but we should probably fix more generally in case a user does something similar.