nested element styles crash

If a dynamic value is placed inline with an element, a nested css block will throw an error.
```imba

name # throws error
css c:cooler5

"name" # no error
css c:cooler5

name # no error
css c:cooler5

"{name}" # no error
css c:cooler8
```
ERROR:
```
× failed with 1 errors [
{
detail: undefined,
location: {
column: 4,
file: 'app/client.imba',
length: 3,
line: 83,
lineText: '\t\t\t\tcss c:cooler5',
namespace: 'file'
},
notes: [],
text: "[imba] Unexpected 'CSS'"
}
```

Start by reproducing the nested CSS examples in app/client.imba, especially the inline dynamic value case that reports Unexpected 'CSS'. Compare it with the quoted and multiline examples; done means the inline form no longer crashes while the other examples continue to compile.

Written by the indexing model from the issue text.