frontend: Fix thumbnail update rate

[Warchamp7]

Description

Fixes thumbnails always updating at the priority speed instead of only when necessary.

Motivation and Context

Thumbnails have a default update speed of 5000ms to maximize performance but are allowed to update every 100ms in certain cases, such as when first loading a thumbnail for a source that does not have one yet, or when something has explicitly requested an update.

The condition for handling the interval change was

    if (!priorityQueue.empty() && !quickUpdate)
// -----^

when it should have been

    if (priorityQueue.empty() && !quickUpdate)

PR fixes the logic but also inverts it to start with the default update interval.

How Has This Been Tested?

👁

Types of changes

• Bug fix (non-breaking change which fixes an issue)

• Performance enhancement (non-breaking change which improves efficiency)

Checklist:

• I have read the contributing document.
• My code has been run through clang-format.
• My code follows the project's style guidelines
• My code is not on the master branch.
• My code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.