This was brought to light by https://tracker.moodle.org/browse/MDL-81060

In the case above, the private files area limit was set to 1mb, so when a teacher uploaded a 22mb scorm, it only partially unzipped (only unzipped 1mb of the files). It then saved "successfully" but when the user went to view it, they get an error message such as:

array_keys argument #1 must of type array, null given

Which is caused by the mdl_scoes rows not generating properly, because the imsmanifest.xml was never unzipped because of the above issue.

In my testing, uploading the same scorm ZIP as an admin (which can bypass the size limit check) generated 88 rows in mdl_files, whereas the same scorm ZIP uploaded by a teacher (which are limited to 1mb by the quota) generated only 8 mdl_files rows.

Ideally when saving the mod_form, it should attempt to unzip and throw an exception or validation error if it fails to unzip.