Display '<empty>' for U8a which is isEmpty (not the default) (#716)

packages/ui-params/src/valueToText.tsx

@@ -7,6 +7,7 @@ import './Params.css';
 import React from 'react';
 import { classes } from '@polkadot/ui-app/util';
 import { isNull, isUndefined, u8aToHex } from '@polkadot/util';
+import { U8a } from '@polkadot/types';
 
 // import IdentityIcon from '@polkadot/ui-react/IdentityIcon';
 // import formatNumber from '@polkadot/ui-app/util/formatNumber';
@@ -150,13 +151,22 @@ function valueToText (type: string, value: any, swallowError: boolean = true, co
   //   }
   // }
 
+  // dont' even ask, nested ?: ... really?
   return isNull(value) || isUndefined(value)
     ? unknown
     : div(
       {},
       ['Bytes', 'Data'].includes(type)
         ? u8aToHex(value.toU8a(true), contentShorten ? 512 : -1)
-        : value.toString()
+        : (
+          value instanceof U8a
+            ? (
+              value.isEmpty
+                ? '<empty>'
+                : value.toString()
+            )
+            : value.toString()
+        )
     );
 }