serde.rs: str_option: Fix type infer error (#670) #1032

Job	Run time
Check file formatting and style	1m 12s
Check documentation	57s
Fuzz Tests	1m 4s
Dependency Tests (stable)	3m 1s
Check minimum rust version	2m 46s
Dependency Tests (beta)	3m 15s
Database Tests - MySQL (stable)	1m 10s
Database Tests - PostgreSQL (stable)	2m 37s
Database Tests - MySQL (beta)	1m 20s
Standard Tests (stable)	2m 29s
Database Tests - PostgreSQL (beta)	2m 46s
Standard Tests (beta)	2m 22s
Database Tests	1s
Test	1s
Pass	1s
	25m 2s

Provide feedback