fix: ignore deleted files in submissions

If a file is deleted from disk somehow
after the student response has been submitted,
the api will still respond with metadata about these files.
However, the download url will be empty,
resulting in broken files in the frontend ui:
the preview pane will display an "Unknown error",
and downloading the files will result in downloaded files
with the correct file names but invalid content.

The student view in ORA handles these deleted files
by simply ignoring them and not displaying them to the user.
So here we do the same:
simply filter out any deleted files from the api.

Private-ref: https://tasks.opencraft.com/browse/BB-9781

Author: samuelallan72

src/data/services/lms/api.js

@@ -52,7 +52,15 @@ const fetchSubmission = (submissionUUID) => get(
     [paramKeys.oraLocation]: locationId(),
     [paramKeys.submissionUUID]: submissionUUID,
   }),
-).then(response => response.data);
+).then(response => ({
+  ...response.data,
+  response: {
+    ...response.data.response,
+    // The API includes metadata for deleted files (without a download url);
+    // we don't want to deal with deleted files here, so filter them out like the student view does.
+    files: response.data.response.files.filter((file) => file.downloadUrl),
+  },
+}));
 
 /**
  * get('/api/submission/files', { oraLocation, submissionUUID })
@@ -65,7 +73,12 @@ const fetchSubmissionFiles = (submissionUUID) => get(
     [paramKeys.oraLocation]: locationId(),
     [paramKeys.submissionUUID]: submissionUUID,
   }),
-).then(response => response.data);
+).then(response => ({
+  ...response.data,
+  // The API includes metadata for deleted files (without a download url);
+  // we don't want to deal with deleted files here, so filter them out like the student view does.
+  files: response.data.files.filter((file) => file.downloadUrl),
+}));
 
 /**
  * fetches the current grade, gradeStatus, and rubricResponse data for the given submission