Symmetry icon should only be displayed if symmetry info is present, otherwise not shown

[blokhin]

Suggested code for https://github.com/tilde-lab/cifplayer/blob/master/player/player.view.web.ts#L469 does not work, symmetry icon is never shown, even for those structures which actually do contain symmetry.

if( !this.structure_3d_data().cell_matrix ) return []

return [
  this.Info(), 
  ... this.symlabel() ? [ this.Symlabel() ] : [],
  this.Center(),
]

[stan-donarise]

Question related to this issue: Is it correct that the symlabel hidden when mpds_data==true? https://github.com/tilde-lab/cifplayer/blob/mpds/src/js/app/main.js#L179

[blokhin]

@stan-donarise yes, correct, please, let's keep it.