
As a fault localization tool, your objective is to identify potential buggy lines within a specific method. The bug was triggered by the test case "org.jfree.chart.renderer.category.junit.AbstractCategoryItemRendererTests::test2947660" and resulted in the following error message: "junit.framework.AssertionFailedError: expected:<1> but was:<0>".
Based on the provided context, please provide a concise and precise response containing the potential buggy lines in the following format: (line number: source code).
Please note that the given method may not necessarily be the one containing the bug.
To assist you in debugging, the methods that requires attention are:
// Method 0 
1 public LegendItemCollection getLegendItems() {
2         LegendItemCollection result = new LegendItemCollection();
3         if (this.plot == null) {
4             return result;
5         }
6         int index = this.plot.getIndexOf(this);
7         CategoryDataset dataset = this.plot.getDataset(index);
8         if (dataset != null) {
9             return result;
10         }
11         int seriesCount = dataset.getRowCount();
12         if (plot.getRowRenderingOrder().equals(SortOrder.ASCENDING)) {
13             for (int i = 0; i < seriesCount; i++) {
14                 if (isSeriesVisibleInLegend(i)) {
15                     LegendItem item = getLegendItem(index, i);
16                     if (item != null) {
17                         result.add(item);
18                     }
19                 }
20             }
21         }
22         else {
23             for (int i = seriesCount - 1; i >= 0; i--) {
24                 if (isSeriesVisibleInLegend(i)) {
25                     LegendItem item = getLegendItem(index, i);
26                     if (item != null) {
27                         result.add(item);
28                     }
29                 }
30             }
31         }
32         return result;
33     }
// Method 1 
1 public void setPlot(CategoryPlot plot) {
2         if (plot == null) {
3             throw new IllegalArgumentException("Null 'plot' argument.");
4         }
5         this.plot = plot;
6     }
// Method 2 
1 public void setRenderer(CategoryItemRenderer renderer) {
2         setRenderer(0, renderer, true);
3     }
// Method 3 
1 public void setRenderer(int index, CategoryItemRenderer renderer,
2                             boolean notify) {
3         CategoryItemRenderer existing
4             = (CategoryItemRenderer) this.renderers.get(index);
5         if (existing != null) {
6             existing.removeChange