Breaking: #67545 - PreFileAdd signal behaviour changed
See forge#67545
Description
In order to check whether an uploaded file exists already before uploading or to determine user preferences about present
files only when needed, the final name of the file is needed. As the final name can be altered by the Pre signal,
which originally always received the temporary uploaded file path as parameter, the signal will now receive an empty string
in $source.
Impact
All Pre slot methods that depend on the $source param must be adapted to handle the new empty string value.
Affected Installations
All extensions that use the Pre signal and depend on the $source param.