some backup fixes

app/src/main/java/ru/vtosters/lite/ui/fragments/OtherFragment.java

@@ -11,6 +11,7 @@ import static ru.vtosters.lite.utils.SettBackup.backupOnlines;
 import static ru.vtosters.lite.utils.SettBackup.backupSettings;
 import static ru.vtosters.lite.utils.SettBackup.deletePrefs;
 import static ru.vtosters.lite.utils.SettBackup.restoreBackup;
+import static ru.vtosters.lite.utils.Themes.getAlertStyle;
 
 import android.content.ClipData;
 import android.content.ClipboardManager;
@@ -75,7 +76,11 @@ public class OtherFragment extends MaterialPreferenceToolbarFragment{
     public static class onlines implements Preference.OnPreferenceClickListener{
         @Override // android.support.v7.preference.Preference.c
         public boolean onPreferenceClick(Preference preference){
-            backupOnlines();
+            try {
+                backupOnlines();
+            } catch (IOException e) {
+                e.printStackTrace();
+            }
             return true;
         }
     }
@@ -171,7 +176,7 @@ public class OtherFragment extends MaterialPreferenceToolbarFragment{
         public boolean onPreferenceClick(Preference preference){
             var arr = SettBackup.getBackupsNames();
             var adapter = new ArrayAdapter(getContext(), android.R.layout.simple_list_item_1, arr);
-            new AlertDialog.Builder(getContext())
+            new AlertDialog.Builder(getContext(), getAlertStyle())
                     .setTitle("Выберите бэкап")
                     .setAdapter(adapter, (dialog, which) -> {
                         try {

app/src/main/java/ru/vtosters/lite/utils/SettBackup.java

@@ -39,7 +39,12 @@ public class SettBackup{
         file.delete();
     }
 
-    public static void backupOnlines(){
+    public static void backupOnlines() throws IOException{
+        if (getPrefContent("onlines.xml") == null) {
+            Toast.makeText(getContext(), "Нет данных для резервного копирования", LENGTH_SHORT).show();
+            return;
+        }
+
         SimpleDateFormat dateFormat = new SimpleDateFormat("yyyyMMdd_HHmmss", Locale.getDefault());
         var dir = new File(getExternalStoragePublicDirectory(DIRECTORY_DOWNLOADS), "/VTLBackups/");
         var file = new File(dir, "Onlines_" + dateFormat.format(new Date()) + ".xml");
@@ -58,9 +63,7 @@ public class SettBackup{
     public static void backupSettings(){
         SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd:HH-mm-ss", Locale.getDefault());
         var file = new File(sBackupDir,
-                "Backup_"
-                + dateFormat.format(new Date())
-                        + ".xml");
+                "Backup_" + dateFormat.format(new Date()) + ".xml");
         try {
             file.delete();
             sBackupDir.mkdirs();