bugfix：没有可见的单元格可能之前就已经有渲染的了

src/base/grid/grid.js

@@ -130,9 +130,9 @@ BI.GridView = BI.inherit(BI.Widget, {
             var visibleColumnIndices = this._columnSizeAndPositionManager.getVisibleCellRange(width, scrollLeft);
             var visibleRowIndices = this._rowSizeAndPositionManager.getVisibleCellRange(height, scrollTop);
 
-            if (BI.isEmpty(visibleColumnIndices) || BI.isEmpty(visibleRowIndices)) {
+            var renderedCells = [], renderedKeys = {}, renderedWidgets = {};
-                return;
+            // 没有可见的单元格就干掉所有渲染过的
-            }
+            if (!BI.isEmpty(visibleColumnIndices) && !BI.isEmpty(visibleRowIndices)) {
                 var horizontalOffsetAdjustment = this._columnSizeAndPositionManager.getOffsetAdjustment(width, scrollLeft);
                 var verticalOffsetAdjustment = this._rowSizeAndPositionManager.getOffsetAdjustment(height, scrollTop);
 
@@ -164,7 +164,6 @@ BI.GridView = BI.inherit(BI.Widget, {
                     return;
                 }
 
-            var renderedCells = [], renderedKeys = {}, renderedWidgets = {};
                 var minX = this._getMaxScrollLeft(), minY = this._getMaxScrollTop(), maxX = 0, maxY = 0;
                 var count = 0;
                 for (var rowIndex = rowStartIndex; rowIndex <= rowStopIndex; rowIndex++) {
@@ -225,6 +224,7 @@ BI.GridView = BI.inherit(BI.Widget, {
                         count++;
                     }
                 }
+            }
             // 已存在的， 需要添加的和需要删除的
             var existSet = {}, addSet = {}, deleteArray = [];
             BI.each(renderedKeys, function (i, key) {