Binding with fedora

[adam-vessey]

In Islandora/islandora#742, explicit references to configuration of Fedora in were made in code, causing warnings should a system be setup and configured without it.

[adam-vessey]

Discussed during the 2020-09-02 I8 tech call. @elizoller pointed out the use of the set property in https://github.com/Islandora/Alpaca/blob/f4af9b97475cf2b64822836be6f65a7453b537c1/islandora-indexing-fcrepo/src/main/java/ca/islandora/alpaca/indexing/fcrepo/FcrepoIndexer.java#L152

Discussion seemed to indicate that an isset() check around the access should be sufficient, with anything downstream which expects the value to be there should be made to deal with its existence.

[jordandukart]

This has popped in the D9 sprint as PHP 7.4 now throws warnings when encountering this: https://www.php.net/manual/en/migration74.incompatible.php#migration74.incompatible.core.non-array-access.