parser: fix not throwing error in some cases

[belochub]

Fix not throwing error when parsing arrays and objects that have no closing brackets and objects that have empty values for some of the keys.

Examples of such cases:

• '[42,' was parsed as [ 42 ].
• '{key:', '{' and '{key:,}' were parsed as {}.

[belochub]

@aqrln, I fixed the typo you mentioned and added some test cases for this fix, PTAL.

[belochub]

Landed in https://github.com/metarhia/JSTP/commit/27675537261f88b8a9a9d488facae5f515f3007e.