Fix panics in the grid algorithm #2265

Job	Run time
Clippy	30s
Documentation	25s
Build Benchmarks (w/ yoga)	44s
Build Benchmarks	32s
Test Fixture Formatting	11s
Rustfmt	11s
Markdown Lint	3s
Test Suite [alloc + all algorithms]	1m 49s
Test Suite [std + block)]	1m 43s
Build [debug feature]	6s
Test Suite [default features]	1m 22s
Test Suite [default except content_size]	1m 29s
Test Suite [default + serde]	1m 32s
Test Suite [std + flexbox]	1m 49s
Test Suite [std + grid]	1m 28s
Test Suite [alloc + no algorithms]	1m 35s
MSRV Build [Rust 1.65]	1m 44s
Test Suite [std (no algorithms)]	1m 35s
Test Suite [no features]	1m 31s
	20m 19s

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