Fire Works Do Nothing When In On Off Hand.

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We're actually already tracking this issue at MCPE-49356, so I will resolve and link this ticket as a duplicate.

That ticket has already been resolved as Invalid, which means this is not considered a bug and won't be fixed. Please do not leave a comment on the linked ticket.

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Since dual wielding has not been introduced yet into bedrock, the only function for rockets in the off hand is for use in the crossbow.