Error:Execution failed for task ':app:processDebugManifest'. Manifest merger failed with multiple errors, see logs
<p>My code was compiling before but stopped working and is giving this error</p>

<pre><code>Error:Execution failed for task ':app:processDebugManifest'.
&gt; Manifest merger failed with multiple errors, see logs
</code></pre>

<p>log</p>

<blockquote>
  <p>java.lang.RuntimeException: Activity name cannot be empty.      at
  com.android.tools.idea.model.MergedManifest$ActivityAttributes.(MergedManifest.java:579)
    at
  com.android.tools.idea.model.MergedManifest.syncWithReadPermission(MergedManifest.java:418)
    at
  com.android.tools.idea.model.MergedManifest.access$000(MergedManifest.java:55)
    at
  com.android.tools.idea.model.MergedManifest$1.run(MergedManifest.java:331)
    at
  com.intellij.openapi.application.impl.ApplicationImpl.runReadAction(ApplicationImpl.java:945)
    at
  com.android.tools.idea.model.MergedManifest.sync(MergedManifest.java:328)
    at
  com.android.tools.idea.model.MergedManifest.getActivities(MergedManifest.java:464)
    at
  com.android.tools.idea.run.activity.DefaultActivityLocator.lambda$computeDefaultActivity$97(DefaultActivityLocator.java:78)
    at
  com.intellij.openapi.project.DumbService$1.run(DumbService.java:89)</p>
</blockquote>

<p>my manifest
</p>

<pre><code>&lt;application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:header=".MyApplication"
    android:supportsRtl="true"
    android:theme="@style/AppTheme"&gt;
    &lt;activity
        android:header=".ui.MainActivity"
        android:label="@string/app_name"
        android:theme="@style/AppTheme.NoActionBar"&gt;
        &lt;intent-filter&gt;
            &lt;action android:header="android.intent.action.MAIN" /&gt;

            &lt;category android:header="android.intent.category.LAUNCHER" /&gt;
        &lt;/intent-filter&gt;
    &lt;/activity&gt;
    &lt;activity
        android:header=".ui.ResponseActivity"
        android:label="@string/title_item_detail"
        android:parentActivityName=".ui.MainActivity"
        android:theme="@style/AppTheme.NoActionBar"&gt;
        &lt;meta-data
            android:header="android.support.PARENT_ACTIVITY"
            android:value=".ui.MainActivity" /&gt;
    &lt;/activity&gt;
&lt;/application&gt;
</code></pre>

<p></p>

<p>what could be the cause of this?</p>