fix handling connection error

app/src/main/java/it/unisannio/ding/ids/wedroid/app/view/BoardViewActivity.java

@@ -148,14 +148,16 @@ public class BoardViewActivity extends AppCompatActivity {
                     ArrayAdapter<String> adapter = new ArrayAdapter<>(getApplicationContext(),
                             android.R.layout.simple_list_item_1, labelsTitle);
                     listView.setAdapter(adapter);
+                    getListsButton.setEnabled(true);
                 }
             }
 
             @Override
             public void onFailure(@NotNull Call<Board> call, @NotNull Throwable t) {
                 Toast.makeText(getApplicationContext(),
-                        getApplicationContext().getString(R.string.board_deleted),
+                        "connection error",
                         Toast.LENGTH_LONG).show();
+                getListsButton.setEnabled(false);
             }
         });
     }