Error: `Cannot read property removeChild of undefined/null expression`

[dwieringa]

In production, I have Rollbar sometimes reporting Cannot read property removeChild of undefined/null expression from the following line:

https://github.com/polonel/SnackBar/blob/507e661b9db204da49a6236680c73612ff85a9e8/src/js/snackbar.js#L129

I noticed that the other reference to removeChild first verifies that the parentElement is defined. This one does not.

I don't have time to submit a PR at the moment, but thought I would capture this in case others run into the same thing or someone has time fix.