Rebase flatpak-indexer to include robustness improving upstream commits
    
    git shortlog 665c80047a7c15145faa8d77b60fadd2feebb1e1..be75c716bae720c45e720f8e1cecab01f4355bd3
    Owen W. Taylor (4):
          Make code to handle disconnections shared between DeltaGenerator and Differ
          Indexer: Remove unchanged-registry-data short-circuit
          Cleaner: check for and remove dangling tardiff:result objects
          Differ: Handle the case where a queued task references a missing spec