Fix MainSwitchPreference crash on Android L

Bug: 312871533
Test: manual
Change-Id: I7d1c1b52c4de670a415330a57a5545020c72521b
diff --git a/packages/SettingsLib/MainSwitchPreference/AndroidManifest.xml b/packages/SettingsLib/MainSwitchPreference/AndroidManifest.xml
index 4b3acbf..e70114f 100644
--- a/packages/SettingsLib/MainSwitchPreference/AndroidManifest.xml
+++ b/packages/SettingsLib/MainSwitchPreference/AndroidManifest.xml
@@ -17,5 +17,5 @@
 
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
           package="com.android.settingslib.widget.mainswitch">
-
+    <uses-sdk android:minSdkVersion="21" />
 </manifest>