fix(cve-whitelist): fix panic in `Get` method of whitelist manager
fix(cve-whitelist): fix panic in `Get` method of whitelist manager

Closes #11951

Signed-off-by: He Weiwei <c834efa4898f8bf976e231f3903babf913725c68@vmware.com>

wy65701436/harbor,reasonerjt/harbor,reasonerjt/harbor,wy65701436/harbor,reasonerjt/harbor,reasonerjt/harbor,wy65701436/harbor,reasonerjt/harbor,wy65701436/harbor,reasonerjt/harbor,wy65701436/harbor,wy65701436/harbor