assets/revision/diff-utils: Fix text selection in revision view
assets/revision/diff-utils: Fix text selection in revision view

Modifying view URL fragment without proper checks had the side effect of
scrolling the view and thus preventing text selection.

Surprisingly, that bug only occured on Firefox.

SoftwareHeritage/swh-web-ui,SoftwareHeritage/swh-web-ui,SoftwareHeritage/swh-web-ui