fix(core): support provide empty icon value

[splincode]

I want pass empty icons for screenshot testing

tuiIconsProvider({
  '@tui.heart': ''
})

[lumberjack-bot]

Pull request was closed ✔️

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[github-actions]

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[bundlemon]

BundleMon

Files updated (1)

Status	Path	Size	Limits
✅	demo/browser/styles.(hash).css	16.27KB (-132B -0.79%)	+10%

Unchanged files (4)

Status	Path	Size	Limits
✅	demo/browser/main.(hash).js	295KB	+10%
✅	demo/browser/vendor.(hash).js	247.33KB	+10%
✅	demo/browser/runtime.(hash).js	43.08KB	+10%
✅	demo/browser/polyfills.(hash).js	11.18KB	+10%

Total files change -131B -0.02%

Unchanged groups (1)

Status	Path	Size	Limits
✅	demo/browser/*..js	7.13MB	-

Final result: ✅

View report in BundleMon website ➡️

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