HPCC-9966 Graph control disappears when switching HTML tabs

Fixes HPCC-9966

Signed-off-by: Gordon Smith <gordon.smith@lexisnexis.com>
Merge pull request #4975 from GordonSmith/HPCC-9966

HPCC-9966 Graph control disappears when switching HTML tabs

Reviewed-By: Miguel Vazquez <miguel.vazquez@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>