How to reproduce:
1. Build the attached project for iOS
2. Run the app on the device
3. Press "Play" button
4. In order showed below, keep quickly pressing on the:
- Input field
- Dictation button
- On background to close the keyboard
(screenshots attached)
5. If the music is still playing, repeat step 4

Actual result: AudioSource stops playing (AudioSource.isPlaying is true and AudioSource.mute is false)
Expected result: AudioSource keeps playing.

Reproducible with: 2017.4.30f1, 2018.4.6f1, 2019.1.14f1, 2019.2.1f1, 2019.3.0a12, 2020.1.0a1.

Tested with:

Reproducible:
- iPhone 7 (iOS 10.12)
- iPhone XS (iOS 12.1)

Not reproducible:
- VLNQA00125, Google Pixel 2 (Pixel 2), Android 8.1.0, CPU: Snapdragon 835 MSM8998, GPU: Adreno (TM) 540

Notes:
- Issue doesn't reproduce on Android.
- The sound is playing again once the program is re-opened.