Fix bottom white space

[Axrorxoja]

No description provided.

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[Axrorxoja]

@googlebot I signed it!

[zhouyiself]

IIRC matching container's height forcibly will cause the camera frame distortion if the aspect ratio of camera preview is different than the container. For example, camera ratio is 16 : 9 and container ratio is 17 : 9, then this change will stretch the camera frame to have ratio 17 : 9.