"Unclosed block" error when checking nested CSS

Given a file with the following contents:

```css
div {
input {
color: black;
}
}
```

The following problem happens

```bash
doiuse --browsers "> 1%" test.css
Error parsing file
file:${MY_NPM_INSTALL}/npm/lib/node_modules/doiuse/bin/cli.js:151
throw error;
^

CssSyntaxError: ${PROJECT_FOLDER}/styles/test.css:1:1: Unclosed block
at Input.error (${MY_NPM_INSTALL}//npm/lib/node_modules/doiuse/node_modules/postcss/lib/input.js:93:16)
at Parser.unclosedBlock (${MY_NPM_INSTALL}//npm/lib/node_modules/doiuse/node_modules/postcss/lib/parser.js:574:22)
at Parser.endFile (${MY_NPM_INSTALL}//npm/lib/node_modules/doiuse/node_modules/postcss/lib/parser.js:336:35)
at Parser.parse (${MY_NPM_INSTALL}//npm/lib/node_modules/doiuse/node_modules/postcss/lib/parser.js:475:10)
at parse (${MY_NPM_INSTALL}//npm/lib/node_modules/doiuse/node_modules/postcss/lib/parse.js:11:12)
at new LazyResult (${MY_NPM_INSTALL}//share/npm/lib/node_modules/doiuse/node_modules/postcss/lib/lazy-result.js:133:16)
at Processor.process (${MY_NPM_INSTALL}/npm/lib/node_modules/doiuse/node_modules/postcss/lib/processor.js:53:14)
at RuleUsageTransform._transform (file:${MY_NPM_INSTALL}//npm/lib/node_modules/doiuse/lib/stream/RuleUsageTransform.js:68:29)
at Transform._write (node:internal/streams/transform:175:8)
at writeOrBuffer (node:internal/streams/writable:556:12) {
reason: 'Unclosed block',
file: '${PROJECT_FOLDER}/styles/test.css',
line: 1,
column: 1,
input: {
column: 1,
endColumn: undefined,
endLine: undefined,
line: 1,
source: 'div {\n input {\n color: black;\n }',
url: 'file: ${PROJECT_FOLDER}/styles/test.css',
file: ' ${PROJECT_FOLDER}/styles/test.css'
}
}
```

## System information

doiuse v6.0.2
Node.js v20.10.0
Ubuntu 23.10