In the case when the conf is as follows:
indentation:
spaces: consistent
indent-sequences: true
and there is no indented block before the first block sequence, and this
block sequence is not indented, then the spaces number is computed as
zero (while it obviously shouldn't be).
This causes such a document to fail on 4th line, instead of 2nd:
a:
- b
c:
- d
This commit fixes that, and adds corresponding tests.
Fixes: #39