Fix parser error messages for inputs with more than a query

[Qup42]

For inputs that consist of a valid SELECT or CONSTRUCT query that are followed by additional (illegal) characters, like

SELECT * WHERE {} } # trailing }

an internal assertion that was not very helpful was triggered. This is now fixed, the error now is "... expected EOF" with the end of the correctly parsed query being highlighted.

The reason was a subtle bug in the SPARQL grammar file.
Closes #1402

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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