Fix replay canvas

The canvas in the replay part of the site, which is supposed to enable switching the observers POV instead causes an error which crashes the frontend application.

created branch 4-fix-replay-canvas

mentioned in merge request !3 (merged)

created branch 4-fix-replay-canvas-2

mentioned in merge request !4 (closed)

closed via merge request !3 (merged)

mentioned in commit e694aeaa