fix: Parse indented newlines correctly

[charithe]

Fixes the case where an indented newline causes invalid parse results.

Consider the following input where the second line contains an indented new line.

a:·b␊
···␊
c:·d␊

Before this fix, the parser produces the following:

a: null
b
c: d

With this fix, the output is as expected.

a: b
c: d

Before submitting your PR, please confirm the following.

• [x] Describe the purpose for which you created this PR.
• [x] Create test code that corresponds to the modification

[charithe]

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