pkg/symbolizer: Fix parser handling of small hex values #17563

Job	Run time
aux	3m 32s
build	3m 12s
old	6m 52s
dashboard	2m 47s
race	7m 17s
race_dashboard	3m 34s
gvisor	3m 52s
arch (presubmit_arch_freebsd)	6m 14s
arch (presubmit_arch_openbsd)	3m 42s
arch (presubmit_arch_darwin)	3m 41s
arch (presubmit_arch_linux)	10m 38s
arch (presubmit_arch_windows)	3m 35s
arch (presubmit_arch_netbsd)	3m 51s
arch (presubmit_arch_executor)	3m 23s
	1h 6m 10s

Provide feedback