Fix Create a reward event for the proposer Cannot get validator account

[cancer-chain]

Summary

when creating proposer event, commission event, reward event, can not get validator account

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Targeted PR against correct branch
• Linked to Github issue with discussion.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Re-reviewed Files changed in the Github PR explorer
• Review Codecov Report in the comment section below once CI passes