Fixed an unsafe case in update liquidity

[jalextowle]

Fixes: #550.

[github-actions]

Hyperdrive Gas Benchmark

Benchmark suite	Current: bfdec2e	Previous: b63be36	Deviation	Status
addLiquidity: min	807 gas	785 gas	2.8025%	🚨
addLiquidity: avg	43878 gas	43434 gas	1.0222%	🚨
addLiquidity: max	80546 gas	80573 gas	-0.0335%	✅
checkpoint: min	514 gas	514 gas	0%	🟰
checkpoint: avg	23181 gas	22776 gas	1.7782%	🚨
checkpoint: max	34040 gas	32767 gas	3.8850%	🚨
closeLong: min	852 gas	852 gas	0%	🟰
closeLong: avg	45870 gas	45661 gas	0.4577%	🚨
closeLong: max	85951 gas	85364 gas	0.6876%	🚨
closeShort: min	809 gas	809 gas	0%	🟰
closeShort: avg	42266 gas	40623 gas	4.0445%	🚨
closeShort: max	87386 gas	86896 gas	0.5639%	🚨
initialize: min	714 gas	714 gas	0%	🟰
initialize: avg	159447 gas	159390 gas	0.0358%	🚨
initialize: max	233486 gas	233486 gas	0%	🟰
openLong: min	740 gas	740 gas	0%	🟰
openLong: avg	112412 gas	112220 gas	0.1711%	🚨
openLong: max	179317 gas	179317 gas	0%	🟰
openShort: min	804 gas	782 gas	2.8133%	🚨
openShort: avg	152236 gas	151781 gas	0.2998%	🚨
openShort: max	219084 gas	218825 gas	0.1184%	🚨
removeLiquidity: min	784 gas	762 gas	2.8871%	🚨
removeLiquidity: avg	57194 gas	57136 gas	0.1015%	🚨
removeLiquidity: max	119628 gas	118973 gas	0.5505%	🚨

This comment was automatically generated by workflow using github-action-benchmark.

[jrhea]

A couple of comments to consider, but overall lgtm

[coveralls]

coverage: 98.524% (+2.7%) from 95.818% when pulling bfdec2e on jalextowle/bug/unsafe-cast-update-liquidity into 640acc1 on main.