merge from 2.0.x - fix the IAE when valueClass is null, in some stran…

…ge cases

git-svn-id: https://svn.apache.org/repos/asf/pivot/trunk@1428503 13f79535-47bb-0310-9956-ffa450edef68

wtk/src/org/apache/pivot/wtk/content/TableViewMultiCellRenderer.java

@@ -324,6 +324,7 @@ public void render(Object row, int rowIndex, int columnIndex,
             TableView.CellRenderer cellRenderer = null;
             Class<?> valueClass = (cellData == null ? null : cellData.getClass());
             while (cellRenderer == null
+                && valueClass != null
                 && valueClass != Object.class) {
                 cellRenderer = cellRenderers.get(valueClass);