fix(caching): Avoid checking existence before fetching

[ChristophWurst]

Summary

Following

server/lib/public/ICache.php

Line 59 in ff66104

* @deprecated 9.1.0 Directly read from GET to prevent race conditions

.

The cache might expire between checking for key existence and fetching the value. In this rare case the code continues with a null value when it doesn't expect one.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[pulsejet]

The doc here should be updated to say that null must be returned if the key doesn't exist. Implementions might end up returning something else, e.g. false

server/lib/public/ICache.php

Lines 36 to 42 in ff66104

	/**
	* Get a value from the user cache
	* @param string $key
	* @return mixed
	* @since 6.0.0
	*/
	public function get($key);