Check for tab container existence, see ROOT-6253.
Check for tab container existence, see ROOT-6253.

tc3t/qoot,tc3t/qoot,kirbyherm/root-r-tools,kirbyherm/root-r-tools,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,kirbyherm/root-r-tools,kirbyherm/root-r-tools,tc3t/qoot,tc3t/qoot,tc3t/qoot,kirbyherm/root-r-tools,tc3t/qoot,kirbyherm/root-r-tools,kirbyherm/root-r-tools