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.
