Fix program indexing logic when cache is empty

[VictoriousRaptor]

#2508 (comment)

Reindex during initializing Program Plugin, when win32 OR uwp cache is empty, instead of both are empty.

Downside: When user choose not to index uwp in plugin settings, reindex is unnecessary.

Not dev only. it's in release as well.

[github-actions]

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Unrecognized words (5)

dlgtitle
flowlauncher
IPlugin
Reloadable
Segoe

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... in a clone of the git@github.com:Flow-Launcher/Flow.Launcher.git repository
on the fix-programs-indexing branch (ℹ️ how do I use this?):

curl -s -S -L 'https://raw.githubusercontent.com/check-spelling/check-spelling/prerelease/apply.pl' |
perl - 'https://github.com/Flow-Launcher/Flow.Launcher/actions/runs/8498026002/attempts/1'

OR

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@check-spelling-bot apply updates.

Warnings (1)

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ℹ️ Warnings	Count
ℹ️ non-alpha-in-dictionary	10

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