fix empty strings

Signed-off-by: Hadi <112569860+anotherhadi@users.noreply.github.com>

leak-utils/misc/json.go

@@ -40,9 +40,13 @@ func flattenJSON(prefix string, in map[string]any, out map[string]any) {
 				}
 			}
 		default:
+			if child == nil {
+				out[key] = ""
+			} else {
 				out[key] = fmt.Sprintf("%v", child)
 			}
 		}
+	}
 }
 
 func flattenJSONFile(inputFile string, outputFile string) error {