Metadata db insert fails due to NULL value
The MetaDataRepository::createMetaDataRecord() function checks the TYPO3_MODE to decide the value of the cruser_id field.
When this is executed in the Install Tool Standalone context the TYPO3_MODE is BE, but no BE_USER is available.
So this results in NULL being assigned for the cruser_id field.
A subsequent database insert fails because of the column being defined as NOT NULL.
This leads to the problem that no metadata records are created for migrated files and the subsequent upgrader adds empty metadata records, lacking the width/height information.