keep the numbers properly formatted at clearing digits

app/src/main/java/calculator/simplemobiletools/com/CalculatorImpl.java

@@ -188,10 +188,7 @@ public class CalculatorImpl {
         else
             newValue = "0";
 
-        if (newValue.equals("-0"))
-            newValue = "0";
-
-        newValue = newValue.replaceAll(",$", "");
+        newValue = formatString(newValue);
         setValue(newValue);
         baseValue = Formatter.stringToDouble(newValue);
     }