_destroyBait needs to check for existence of bait before trying to remove it

[m90]

From looking at the errors in our Sentry setup I can see that there are cases where the bait has already been removed by someone before the library calls the _destroyBait method here:

BlockAdBlock/blockadblock.js

Line 94 in bf4c340

window.document.body.removeChild(this._var.bait);

Failed to execute 'removeChild' on 'Node': The node to be removed is not a child of this node.

Since the library theoretically emits the events after removing the bait, this will never happen in case the above throws.

Ideally the library would simply check if the bait is still in the DOM before trying to remove it.