This patch addresses an edge-case that'll probably never happen, but it nonetheless seems like something that we want to fix.
Note how we're using the `#currentEditor`-field to prevent opening the dialog when it's already active, and it being reset once the dialog has been closed.
By also resetting the `#currentEditor`-field during destruction, instead of waiting until the dialog has actually closed (assuming it's currently open), there's a *tiny* window of time[1] during which we could theoretically allow to (incorrectly) re-open the dialog and thus getting out-of-sync state in the viewer-component.
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[1] Since the "close" event, on a dialog-element, is dispatched asynchronously by the browser.
When the user edit an existing alt-text and remove it, we want to be able
to save this state and consequently remove the done state from the
alt-text button.
Remove the button from its parent when the editor is removed: it should
help to save few Kb of memory.
Radio-buttons can also be toggled by clicking on their associated `label`-elements, and not only the `input`-elements itself, however it seems that "pointerdown" event listeners don't cover that case.
Hence it's possible that telemetry could miss certain cases of a mouse being used, and the easiest solution seem to be to instead use "click" event listeners and just ignore keyboard-based events.
Looking at the save-telemetry values they're all boolean *except* for "alt_text_edit" in one instance, since `this.#previousAltText` may be an empty string (looking at the `editAltText` method) and this value may thus become an empty string as well.
When closing a document in the viewer, e.g. by running `PDFViewerApplication.close()` in the console, the `AltTextManager.#finish` method currently throws *unless* the `altText` dialog is actually open.
Similar to e.g. the PasswordPrompt, we should thus only attempt to close the `altText` dialog when it's open.
