The microphone button becomes greyed out for 4 seconds if it's clicked quickly while the overlay is dismissed

[SoftVision-CarmenFat]

[Affected versions]:

• Firefox 55.0.2 and up
• Voice Fill 1.3.0

[Affected Platforms]:

• All Windows
• All Mac
• All Linux

[Prerequisites]:

• Latest Voice Fill add-on (1.3.0) was previously installed on a clean profile.
• Tools -> Page Info -> Permissions -> Use the Microphone -> "Use Default" is unchecked and "Block" is checked.

[Steps to reproduce]:

1. Open the browser with the profile from prerequisites and navigate to a supported website.
2. Click on the microphone button from the right side of the search input.
3. Quickly click the microphone button as the overlay is dismissed.
4. Observe what happens with the microphone button.

[Expected result]:

• The overlay is triggered again OR
• The microphone button is greyed out until a new session can be started.

[Actual result]:

• The microphone button is greyed out for ~4 seconds.

[Notes]:

• Attaching a screen recording of the issue: