Removed the empty fragment when the back button is pressed. (BUGFIX)

Author: BalioFVFX

simplefileexplorer/src/main/java/com/example/simplefileexplorer/SimpleFileExplorerActivity.java

@@ -5,7 +5,7 @@
 import android.content.Intent;
 import android.content.pm.PackageManager;
 import android.os.Environment;
-import android.support.v4.app.FragmentManager;
+import android.support.v4.app.Fragment;
 import android.support.v4.content.ContextCompat;
 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
@@ -14,6 +14,9 @@
 import android.widget.ImageView;
 import android.widget.Toast;
 
+import java.util.List;
+
+
 public class SimpleFileExplorerActivity extends AppCompatActivity implements ActivityListener{