V4: top bar title color is not reverting back when pop screen

[blueberry6401]

Issue Description

On pushed screen:

static options() {
    return {
      topBar: {
        title: {
          text: 'Pushed Screen',
          color: 'red',
        },
      }
    };
  }

After pop, the top bar title color should back to black.

Environment

• React Native Navigation version: 4.7.1
• React Native version: 0.61.5
• Platform(s) (iOS, Android, or both?): iOS
• Device info (Simulator/Device? OS version? Debug/Release?): iOS 13.