[BUG] (v0.5.x) nil pointer dereference on smart contract custom wasm event

[nzaharov]

Describe the bug
Executing a contract which creates a custom wasm event (introduced in Cosmwasm 0.15.0) causes a runtime panic.
Exception seems to originate from x/wasm/types/connector.go.

To Reproduce
Create and execute a smart contract whose handler returns a Response with one Event, no attributes, no messages and no data.

Context & versions
Reproduced on LocalTerra bombay (Cosmwasm 0.15.0, cosmos-sdk 0.43.0-rc0) and bombay-next branches (Cosmwasm 0.16.0, cosmos-sdk 0.43.0-rc3).

[yun-yeo]

Thanks a lot for reporting.

let me fix this @nzaharov