Only propagate on ConvertToString when there's changes.

app/src/main/java/com/codigoparallevar/minicards/parts/strings/ConvertToString.java

@@ -233,10 +233,12 @@ public class ConvertToString implements Part {
             encoded = value.toString();
         }
 
+        if (!_lastValue.equals(encoded)) {
             _lastValue = encoded;
 
             _stringOutputConnector.send(new StringSignal(encoded));
         }
+    }
 
     @Override
     public String get_id() {