Handle `IconData::default()` without crashing #8724

Job	Run time
cargo-deny aarch64-apple-darwin	43s
cargo-deny aarch64-linux-android	44s
cargo-deny i686-pc-windows-gnu	44s
Check wasm32 + wasm-bindgen	2m 30s
cargo-deny i686-pc-windows-msvc	39s
cargo-deny i686-unknown-linux-gnu	40s
cargo-deny wasm32-unknown-unknown	43s
Format + check + test	6m 1s
cargo-deny x86_64-apple-darwin	39s
cargo-deny x86_64-pc-windows-gnu	42s
cargo-deny x86_64-pc-windows-msvc	39s
android	24s
cargo-deny x86_64-unknown-linux-gnu	36s
Check Windows	2m 39s
cargo-deny x86_64-unknown-linux-musl	40s
cargo-deny x86_64-unknown-redox	41s
	19m 44s

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