Closes #7391: FileNotFound is preloaded for some page templates

[jeawhanlee]

Description

Fixes wp-media/wp-rocket#7391
Fixes the issue when plugin preloads string 'file not found' on page.

Type of change

• New feature (non-breaking change which adds functionality).
• Bug fix (non-breaking change which fixes an issue).

Detailed scenario

What was tested

Check that with specific templates, file not found is added to the db and then preloaded.

How to test

• Test on page using this template: https://github.com/wp-media/rocket-test-data/blob/master/templates/preloadfonts_differentformatsdebug.php
• Check that 'File not found' is not saved to DB and and preloaded on page.

Technical description

Documentation

Updated the logic to only push new font variations when there is a valid matching url:

rocket-scripts/src/BeaconPreloadFonts.js

Lines 520 to 536 in 834d8d0

	if (matchingUrl) {
	// Only create new object if a valid matching url exist in network loaded fonts.
	if (!allFonts[fontFamily]) {
	allFonts[fontFamily] = {
	type: 'hosted',
	variations: [],
	elementCount: {
	aboveFold: aboveElements.length,
	belowFold: belowElements.length,
	total: elements.length
	},
	urlCount: {
	aboveFold: new Set(),
	belowFold: new Set()
	}
	};
	}

This eliminates the need to add a default value assignment directly in the object which in this case is File not found

New dependencies

N/A

Risks

N/A

Mandatory Checklist

Code validation

• I validated all the Acceptance Criteria. If possible, provide screenshots or videos.
• I triggered all changed lines of code at least once without new errors/warnings/notices.
• I implemented built-in tests to cover the new/changed code.

Code style

• I wrote a self-explanatory code about what it does.
• I protected entry points against unexpected inputs.
• I did not introduce unnecessary complexity.
• Output messages (errors, notices, logs) are explicit enough for users to understand the issue and are actionnable.

Unticked items justification

Not applicable to the changes in this PR

Additional Checks

• In the case of complex code, I wrote comments to explain it.
• When possible, I prepared ways to observe the implemented system (logs, data, etc.).
• I added error handling logic when using functions that could throw errors (HTTP/API request, filesystem, etc.)

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
✅ +0.04% (target: -1.00%)	✅ 100.00% (target: 50.00%)

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (65069d9)	1624	1298	79.93%
Head commit (834d8d0)	1627 (+3)	1301 (+3)	79.96% (+0.04%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#56)	37	37	100.00%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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