HPCC-8786 Graph "Advanced/Show SVG" broken

Fixes HPCC-8786

Signed-off-by: Gordon Smith <gordon.smith@lexisnexis.com>
Merge pull request #3954 from GordonSmith/HPCC-8786

HPCC-8786 Graph "Advanced/Show SVG" broken

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>