[PATCH v2 2/5] winegstreamer: Move the conditional cleanup to the create error path.

[Rémi Bernon]

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=51931
Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=52391
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v2: * Refactor the error cleanup path so that the destroy function
       doesn't need to handle partially constructed transform.

     * Small tweaks to the code to make it terser and remove unnecessary
       variables.
-- 
Rémi Bernon <rbernon at codeweavers.com>