Add some security hardening to passed playlist attributes.

Props xknown.
See #26631.


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In the tracklist for playlist, fall back to `title` if there is no `caption`.

Props bassgang.
See #26631.


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`wp.media.collection` should be its own civilized instantiable class, not a wrapper/factory. The class shall contain no reference to specific instances, and shall not try to grab static properties of itself. `self`, meet `this`.

See #26631.


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This comment was pasted and does not apply to specified code block.

See #26631.


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Upgrade Plupload to 2.1.1, props kovshenin, see #25663
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In `media-editor.js`, use `_.isUndefined()` when available.

See #26631.


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Remove debugging cruft, see #25663
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Avoid an undefined index notice in wp_handle_upload().

props tivnet.
fixes #27225.
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Some playlist cleanup:

* Check properties against the `window` object when using `_.isUndefined()` on globals
* Fix a typo for `$safe_type` introduced in [27311]

See #26631.


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Restore / re-tools some docs after [27313].

See #26631.


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Rather than extending `media.controller.CollectionAdd` 3 times, make it a constructor that dynamically extends `media.controller.Library` and use instances of it instead.

See #26631.


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Avoid an undefined index notice in wp_doc_link_parse().

props pross for initial patch.
fixes #27214.
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Remove temporary hooks added in [26865].

fixes #26661.
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Use a consistent format for translator comments.

props GaryJ.
fixes #27228.
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