Fixes issue with parsing whitespace content back from database - fixes #13907

That's actually funny, I wrote the original code that served as a base for this parser [here](https://github.com/dockyard/pg_array_parser/commit/b163938bfd26fa9bde4af9db3814d00ea89bbcee#diff-a94e566f3af5e6328b83bf26177a003b) and it also had the same issue with whitespace that was fixed by [this change](https://github.com/dockyard/pg_array_parser/commit/f5b1ab979555dd9787373e5e6fd031fe3c9a7427), so, here it goes again, hehehe, fixing my own code a second time :D

Included two more tests to make sure this fix stays now. This fixes #13907.