Show "Empty History" only when completely empty.

Fixes: 33107214

Do not show "Empty History" view when there is a Current Expression.

Change-Id: I437fd3c4d71e0d80179365c886078a3499c9c184
diff --git a/src/com/android/calculator2/HistoryFragment.java b/src/com/android/calculator2/HistoryFragment.java
index b16ccdb..e216400 100644
--- a/src/com/android/calculator2/HistoryFragment.java
+++ b/src/com/android/calculator2/HistoryFragment.java
@@ -158,7 +158,7 @@
             for (long i = 0; i < maxIndex; ++i) {
                 newDataSet.add(null);
             }
-            if (maxIndex == 0) {
+            if (newDataSet.isEmpty()) {
                 newDataSet.add(new HistoryItem());
             }
             mDataSet = newDataSet;