RFE: Warn on opening video when multiple videos loaded

[T-buch]

WISH:
Warning on opening when the project contains multiple files

I have tried several times that I was in the process of pasting a number of files together via the append function, but accidentally "clicked" OPEN  instead of  APPEND, whereby everything was lost

[eumagga0x2a]

You should have used "Recent" --> "Restore previous session" right after you accidentally opened instead of appending another video.