Fix: prevent a way to open toolbar on a disabled toolbar editor

**Situation:**
```js
var editor1 = new MediumEditor('#editor1', {});
var editor2 = new MediumEditor('#editor2', {
	disableToolbar: true
});
```

**Reproducing:**
Click two times to select a word on the editor with `disableToolbar`.
Then without releasing the click, move you mouse to the other editor (the one without the `disableToolbar`).
Then release it.

**Result:**
It will open a toolbar on the editor with `disableToolbar`.