Android Studio lỗi Rendering Problems

Mình đang tập tành lập trình android. Nhưng khi chạy thử chương trình đơn giản thì thấy nó hiện lên lỗi như thế mặc dù không thấy chương trình chạy sai gì. Ai giúp mình sửa nó với.

1.png1440x900 157 KB

Đây là stack khi copy ra

java.lang.NullPointerException at android.support.v7.app.WindowDecorActionBar.getDecorToolbar(WindowDecorActionBar.java:241) at android.support.v7.app.WindowDecorActionBar.init(WindowDecorActionBar.java:198) at android.support.v7.app.WindowDecorActionBar.<init>(WindowDecorActionBar.java:190) at sun.reflect.GeneratedConstructorAccessor309.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:422) at org.jetbrains.android.uipreview.ViewLoader.createNewInstance(ViewLoader.java:458) at org.jetbrains.android.uipreview.ViewLoader.loadClass(ViewLoader.java:170) at org.jetbrains.android.uipreview.ViewLoader.loadView(ViewLoader.java:103) at com.android.tools.idea.rendering.LayoutlibCallbackImpl.loadView(LayoutlibCallbackImpl.java:168) at com.android.layoutlib.bridge.bars.AppCompatActionBar.<init>(AppCompatActionBar.java:89) at com.android.layoutlib.bridge.impl.Layout.createActionBar(Layout.java:237) at com.android.layoutlib.bridge.impl.Layout.<init>(Layout.java:151) at com.android.layoutlib.bridge.impl.RenderSessionImpl.inflate(RenderSessionImpl.java:206) at com.android.layoutlib.bridge.Bridge.createSession(Bridge.java:426) at com.android.ide.common.rendering.LayoutLibrary.createSession(LayoutLibrary.java:350) at com.android.tools.idea.rendering.RenderTask$2.compute(RenderTask.java:510) at com.android.tools.idea.rendering.RenderTask$2.compute(RenderTask.java:498) at com.intellij.openapi.application.impl.ApplicationImpl.runReadAction(ApplicationImpl.java:888) at com.android.tools.idea.rendering.RenderTask.createRenderSession(RenderTask.java:498) at com.android.tools.idea.rendering.RenderTask.access$600(RenderTask.java:72) at com.android.tools.idea.rendering.RenderTask$3.call(RenderTask.java:610) at com.android.tools.idea.rendering.RenderTask$3.call(RenderTask.java:607) at com.android.tools.idea.rendering.RenderService.runRenderAction(RenderService.java:362) at com.android.tools.idea.rendering.RenderTask.render(RenderTask.java:607) at com.android.tools.idea.rendering.RenderTask.render(RenderTask.java:629) at com.intellij.android.designer.designSurface.AndroidDesignerEditorPanel$6.run(AndroidDesignerEditorPanel.java:480) at com.intellij.util.ui.update.MergingUpdateQueue.execute(MergingUpdateQueue.java:320) at com.intellij.util.ui.update.MergingUpdateQueue.execute(MergingUpdateQueue.java:310) at com.intellij.util.ui.update.MergingUpdateQueue$2.run(MergingUpdateQueue.java:254) at com.intellij.util.ui.update.MergingUpdateQueue.flush(MergingUpdateQueue.java:269) at com.intellij.util.ui.update.MergingUpdateQueue.flush(MergingUpdateQueue.java:227) at com.intellij.util.ui.update.MergingUpdateQueue.run(MergingUpdateQueue.java:217) at com.intellij.util.concurrency.QueueProcessor.runSafely(QueueProcessor.java:238) at com.intellij.util.Alarm$Request$1.run(Alarm.java:351) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745)