one-way-number-mask types one or many "0" characters in odd circumstances

I've written these two failing tests for `one-way-number-mask-test.js`.

```js
test('It does not input a zero when hitting "."', async function(assert) {
await render(hbs``);
await fillIn('input', '.');

assert.dom('input').hasValue('');
});

test('It does not input a zero when hitting "m"', async function(assert) { // This also happens with the letter `k`
await render(hbs``);
await fillIn('input', 'm');

assert.dom('input').hasValue('');
});
```

Start with the failing cases in one-way-number-mask-test.js and run that test file to reproduce the behavior. Trace how OneWayNumberMask handles ".", "m", and "k" input, then confirm the input remains empty for each case when the tests pass.

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