Refactor UpdateRule method to handle category ID removal correctly.

internal/service/waf.go

@@ -817,7 +817,11 @@ func (s *wafService) UpdateRule(ctx context.Context, req *RuleRequest) error {
 			for i, id := range wafService.RuleCategoryStatus.CategoryID {
 				for _, categoryID := range req.CategoryID {
 					if id == categoryID {
-						wafService.RuleCategoryStatus.CategoryID = append(wafService.RuleCategoryStatus.CategoryID[:i], wafService.RuleCategoryStatus.CategoryID[i+1:]...)
+						if i == len(wafService.RuleCategoryStatus.CategoryID)-1 {
+							wafService.RuleCategoryStatus.CategoryID = wafService.RuleCategoryStatus.CategoryID[:i]
+						} else {
+							wafService.RuleCategoryStatus.CategoryID = append(wafService.RuleCategoryStatus.CategoryID[:i], wafService.RuleCategoryStatus.CategoryID[i+1:]...)
+						}
 					}
 				}
 			}