Feature Index disappearing on map moves

[prushforth]

Steps to reproduce:

Enable feature indexing on extension:

Load this page

Click on the map with your mouse

-- feature index appears

Drag the map \< 1cm

Expected behaviour

-- if reticle encompasses different features, set of features in the index changes accordingly

Observed behaviour:

-- reticle disappears -- feature index disappears

[yhy0217]

Resolved in 1ccf35434019b19c8f83704cf05033cb7d771802 and #873