Missing closing brace in CSS for cosmetic style rules

[antonok-edm]

The generateCosmeticBlockingStylesheet method appears to mistakenly omit a closing brace whenever custom style rules are added to a stylesheet that will be injected into a page.

Existing browser tests perform as expected -- it appears an implicit closing brace is added at the end of the stylesheet. Although custom style rules are uncommon within filter lists; if more than one were added, the stylesheet would become malformed.

The missing closing brace is located here. A unit test should be added to ensure generateCosmeticBlockingStylesheet builds correctly formatted stylesheets when one or more custom style rules are used.

[pes10k]

@antonok-edm can this be closed?