Fix the remaining lint errors in the URL polyfill

[Snuffleupagus]

When switching to ESLint, the yoda rule was temporarily disabled for the URL polyfill.
Those linting errors should be fixed, so that the exception can be removed.

In order to address this issue:

1. Remove lines src/shared/util.js#L1758-L1759 and src/shared/util.js#L2396-L2397.
2. Run linting locally, using gulp lint, to find the errors.
3. Fix the errors reported by ESLint.

For more information about the contributing workflow, please refer to https://github.com/mozilla/pdf.js/wiki/Contributing and https://github.com/mozilla/pdf.js#getting-the-code.