Steps to reproduce:
• open group chat and type a message containing "@" but don't send it.
• tap on + and select last photo/video from the strip.
• observe app crashing.
Cause of crash:
Attempting to access a child view controller of UIPageViewController
while using force unwrap when UIPageViewController's view is not yet loaded.
The fix:
• Remove force unwrapping (linter was complaining about that too).
• Add "isViewLoaded" check to the method that was causing the crash.
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