fix: Improve type error when indexing a variable of unknown type #16425

Job	Run time
yarn-lock	1m 3s
build-nargo	2m 30s
build-noirc-abi	1m 18s
build-acvm-js	1m 22s
build-noir-wasm	3m 31s
Load critical library list	3s
noirc_abi	1m 18s
ACVM JS (Browser)	1m 14s
ACVM JS (Node.js)	44s
Noir JS	1m 12s
noir_codegen	1m 3s
Example scripts	10s
Check external repo - ${{ matrix.project.repo }}	0s
Integration Tests (Browser)	2m 11s
noir_wasm	1m 28s
Integration Tests (Node)	2m 13s
End	1s
	21m 21s

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