.substr() is deprecated so we replace it with .slice() which works similarily but isn't deprecated
Signed-off-by: Tobias Speicher <rootcommander@gmail.com>
## Issue:
Currently, the checkbox grayed-out state is only correctly updated when changing from "no-file" to "file selected". If you have selected a video file and later changed to a text file, the checkbox doesn't gray out.
## Code Changes:
`fileVid` wasn't being updated for the case of non-videos; now it does.
## Issue
4332: Video transcode setting not reflected correctly (MP3 incorrectly transcoded to MP4)
2 issues here:
(1) The checkbox is mixing between user state and logic state.
(2) The variables (e.g. `optimize`, `isVid`, `filePath`, etc) will have values from the previous operation when you enter Publish Page, so GUI issues beyond Transcode can be also produced (e.g. showing Transcode enabled for an image).
## Changes
The "Transcode" checkbox state (checked vs. unchecked) will now reflect the user's desire and will be a persisted state. Whether or not this setting is used will be reflected by the checkbox's grayed-out state (i.e. it can be checked for non videos, but it will be grayed out).
Changed "Your video may not be the best format. Use MP4s in H264/AAC format and a friendly bitrate (720p) for more reliable streaming." to "Your video may not be the best format. Use MP4s in H264/AAC format and a friendly bitrate (under 5 mbps) and resolution (720p) for more reliable streaming." and changed the two times it says this "For video content, use MP4s in H264/AAC format and a friendly bitrate (720p) for more reliable streaming." to "For video content, use MP4s in H264/AAC format and a friendly bitrate (under 5 mbps) and resolution (720p) for more reliable streaming."
