RN: custom emojis are not searchable until they are loaded on the screen via scrolling

Description

Repro:
1. Clear cache on mobile, then connect to community.mattermost
2. On a post, try to add the "help" custom emoji by searching in the reaction picker

Observe that the :help: emoji is not returned with search. But if you manually scroll to the custom emoji section in the picker and let the :help: emoji load on screen, then retry the emoji search, then :help: emoji is returned. See vid

Expected: custom emoji are always returned in search results

QA Test Steps

None

Mana

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Assignee

Unassigned

QA Assignee

None

Reporter

Eric Sethna

Epic Link

None

Fix versions

Mattermost Team

Core Features

Sprint

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QA Testing Areas

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GitHub Issue

None

Components

None

Severity

None
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