HPCC-10974 Visualisation CSS Injection was failing

Fixes HPCC-10974

Signed-off-by: Gordon Smith <gordon.smith@lexisnexis.com>
Merge pull request #5494 from GordonSmith/HPCC-10974

HPCC-10974 Visualisation CSS Injection was failing

Reviewed-By: Miguel Vazquez <miguel.vazquez@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>