"Please enable your microphone to use Voice Fill" message is wrongly displayed after performing multiple voice searches using toolbar's button

[Softvision-CristinaBadescu]

[Affected versions]:

• Firefox 56.0.2 and up
• Voice Fill v.1.3.4.1

[Affected Platforms]:

• All Windows
• All Linux
• All Mac

[Prerequisites]:

• Have a Firefox profile with the Voice Fill (v. 1.3.4.1) experiment installed.
• Tools -> Permissions -> "Use default" is unchecked and "Allow" is checked.

[Steps to reproduce]:

1. Open the browser with the profile from prerequisites.
2. Click the Voice Fill button from the toolbar at least 5 times.
3. Go to the last opened tab and observe the behavior.

[Expected result]:

• The recording session starts.

[Actual result]:

• The "Please enable your microphone to use Voice Fill" message is displayed.

[Notes]:

• The frequency of encountering this issue may vary: 4 or 6 voice searches.
• This issue is also reproducible when using the "Voice Fill" button located in the right side of the search bar.
• This issue is also reproducible if you manually click "Allow" microphone permission for each search.
• Here is a screen recording of the issue:
  

[mrstegeman]

Cannot reproduce.