Improved error message when attempting to create a transaction with no reference transaction (which in practice is the same thing as having a zero balance).

This was previously in the UI repository but wasn't copied over to qortal-ui. It probably didn't make it into any releases yet.

qortal-ui-crypto/api/transactions/TransactionBase.js

@@ -47,6 +47,10 @@ export default class TransactionBase {
             },
             () => {
                 if (!(this._lastReference instanceof Uint8Array && this._lastReference.byteLength == 64)) {
+                    if (this._lastReference == 0) {
+                        // No prior transactions exist
+                        return 'Invalid last reference. Please ensure that you have at least 0.001 QORT for the transaction fee.'
+                    }
                     return 'Invalid last reference: ' + this._lastReference
                 }
                 return true