Suppress pointless warning

Uses features only present in Android 4.4, but the activity only appears
in the shortcut list which isn't exposed for Android prior to 7.1

android-project/app/src/main/java/org/diasurgical/devilutionx/ImportActivity.java

@@ -5,8 +5,10 @@ import android.content.ClipData;
 import android.content.ContentResolver;
 import android.content.Intent;
 import android.net.Uri;
+import android.os.Build;
 import android.support.annotation.Nullable;
 import android.os.Bundle;
+import android.support.annotation.RequiresApi;
 import android.support.v4.provider.DocumentFile;
 import android.util.Log;
 
@@ -20,6 +22,7 @@ public class ImportActivity extends Activity {
 
 	private static final int IMPORT_REQUEST_CODE = 0xD1AB70;
 
+	@RequiresApi(api = Build.VERSION_CODES.KITKAT)
 	@Override
 	protected void onCreate(Bundle savedInstanceState) {
 		super.onCreate(savedInstanceState);
@@ -60,7 +63,7 @@ public class ImportActivity extends Activity {
 		if (fileUri == null)
 			return;
 
-		DocumentFile file = DocumentFile.fromSingleUri(getApplicationContext(), fileUri);
+		DocumentFile file = Objects.requireNonNull(DocumentFile.fromSingleUri(getApplicationContext(), fileUri));
 		String fileName = file.getName();
 		String externalFilesDir = getExternalFilesDir(null).getAbsolutePath();
 		String externalFilesPath = externalFilesDir + "/" + fileName;