8906-Prevented negative seek position

[LuGO0]

0. According to the discussion I saw on Seeking to a negative value makes the ExoPlayer to pause over HLS #8906, tried to resolve this Issue
1. Added Assertion for preventing negative seek position. closes Seeking to a negative value makes the ExoPlayer to pause over HLS #8906

[nick-tkachov]

You can have negative seek position in Live playback if you have content buffered outside of the sliding window.

[LuGO0]

You can have negative seek position in Live playback if you have content buffered outside of the sliding window.

Oops Did not know about it, will read about it more .

[ojw28]

Adding an assertion that'll crash applications if they attempt to pass negative seek positions seems pretty risky to me, and I'm not sure it's the correct solution. Let's use the issue (#8906) for any discussion about the correct solution.