error message is unclear when the right side of files is empty

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My snapcraft.yaml file was missing the '.' and the error I got was unclear:

kati@linux:~/Development/OpenSolitaire.Classic$ snapcraft snap
Skipping pull opensolitaire-classic (already ran)
Preparing to build opensolitaire-classic
Building opensolitaire-classic
'NoneType' object has no attribute 'lstrip'

=== snapcraft.yaml ===
name: opensolitaire-classic
version: 0.9.2
summary: Open Solitaire Classic
description: |
    Pass the time with this classic solitaire game (licensed under GPL-3)

apps:
    run:
        command: OpenSolitaire.Classic

parts:
    opensolitaire-classic:
        plugin: copy
        files:
            "*":
=== end snapcraft.yaml ===

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Kyle Fazzari (kyrofa)]

Fix here: https://github.com/snapcore/snapcraft/pull/1096