standardize empty string to String::default()

This replaces "".to_owned() "".to_string() and String::from("")

src/client/result/EmailAddressParsedResult.rs

@@ -55,8 +55,8 @@ impl EmailAddressParsedRXingResult {
             vec![to],
             Vec::new(),
             Vec::new(),
-            "".to_owned(),
-            "".to_owned(),
+            String::default(),
+            String::default(),
         )
     }