"Show whitespace changes" is shown if the URL parameter is present at all

https://gitlab.com/gitlab-org/gitlab-ee/blob/b5757b49695af96cfa47ab0f047298c094eb438d/app/assets/javascripts/diffs/components/changed_files.vue#L34-36 seems to check if the w URL parameter is present at all. However, when toggling the setting off via the button, we simply change the parameter value to 0 rather than removing it entirely.

This causes the button to always show "Show whitespace changes" even when w=0 is appended to the URL.