Dropping a file doesn't close the overlay directly

[NeoCoderMatrix86]

Describe the bug
The file overlay is not closed directly, when a file gets dropped. Therefore the user doesn't see the loading animation and also could click to add a file.

EDGE Exception:

Uncaught NotFoundError: Failed to execute 'removeChild' on 'Node': The node to be removed is not a child of this node.
    at t (contentStart.js:1:249)
    at e.onload (contentStart.js:1:725)
content.js:1  Uncaught TypeError: this.drop is not a function
    at Object.handleEvent (content.js:1:14068)