Merge pull request #502 from kongzue/codex/add-junit-test-for-dialoglistbuilder

Add DialogListBuilder clear() unit test

DialogX/src/main/java/com/kongzue/dialogx/util/DialogListBuilder.java

@@ -69,6 +69,8 @@ public class DialogListBuilder {
     }
 
     public void clear() {
-        dialogs.clear();
+        if (dialogs != null) {
+            dialogs.clear();
+        }
     }
 }

DialogX/src/test/java/com/kongzue/dialogx/util/DialogListBuilderTest.java

@@ -0,0 +1,13 @@
+import com.kongzue.dialogx.util.DialogListBuilder;
+import org.junit.Test;
+
+import static org.junit.Assert.assertTrue;
+
+public class DialogListBuilderTest {
+    @Test
+    public void clearOnEmptyListDoesNotThrow() {
+        DialogListBuilder builder = new DialogListBuilder();
+        builder.clear();
+        assertTrue(builder.isEmpty());
+    }
+}