[BUG] other flow rules should act on empty origin

other flow rules should act on empty origin, otherwise the resource annotated with @SentinelResource will not be restricted by other rules.

in FlowRuleManager
```
public static boolean isOtherOrigin(String origin, String resourceName) {
if (StringUtil.isEmpty(origin)) {
return false;
}
```

Start in FlowRuleManager at the isOtherOrigin method shown in the issue and trace how an empty origin is handled for @SentinelResource flow rules. Confirm the intended behavior for empty origins and verify that other flow rules can restrict the annotated resource when the change is complete.

Written by the indexing model from the issue text.