Cannot use speech synthesis sim after deleting text

[jamesadevine]

Steps to reproduce:

1) goto https://microsoft.github.io/jacdac-ts/dashboard/ 2) add speech synthesis simulator 3) delete text from simulator 4) try to enter new text

Expected behaviour

The user is able to enter any text they want for the reader to read out.

Actual behaviour

After deleting all text, the text field is no longer editable.

[pelikhan]

Fixed.