handle FileDisplayActivity openFileByPath request failed (e.g. file deleted)

Signed-off-by: Jonas Mayer <jonas.a.mayer@gmx.net>

app/src/main/java/com/owncloud/android/ui/activity/FileDisplayActivity.java

@@ -2507,8 +2507,7 @@ public class FileDisplayActivity extends FileActivity
         setUser(user);
 
         if (fileId == null) {
-            dismissLoadingDialog();
-            DisplayUtils.showSnackMessage(this, getString(R.string.error_retrieving_file));
+            onFileRequestError(null);
             return;
         }
 
@@ -2529,8 +2528,7 @@ public class FileDisplayActivity extends FileActivity
         setUser(user);
 
         if (filepath == null) {
-            dismissLoadingDialog();
-            DisplayUtils.showSnackMessage(this, getString(R.string.error_retrieving_file));
+            onFileRequestError(null);
             return;
         }
 
@@ -2544,8 +2542,7 @@ public class FileDisplayActivity extends FileActivity
         try {
             client = clientFactory.create(user);
         } catch (ClientFactory.CreationException e) {
-            dismissLoadingDialog();
-            DisplayUtils.showSnackMessage(this, getString(R.string.error_retrieving_file));
+            onFileRequestError(null);
             return;
         }
 
@@ -2554,9 +2551,16 @@ public class FileDisplayActivity extends FileActivity
                                                                     client,
                                                                     storageManager,
                                                                     user);
-        asyncRunner.postQuickTask(getRemoteFileTask, this::onFileRequestResult, null);
+        asyncRunner.postQuickTask(getRemoteFileTask, this::onFileRequestResult, this::onFileRequestError);
+    }
+
+    private Unit onFileRequestError(Throwable throwable) {
+        dismissLoadingDialog();
+        DisplayUtils.showSnackMessage(this, getString(R.string.error_retrieving_file));
+        return null;
     }
 
+
     private Unit onFileRequestResult(GetRemoteFileTask.Result result) {
         dismissLoadingDialog();