Trying to open a subworkflow sometimes fails.

For some workflows, trying to open a subworkflow fails when double-clicking in the diagram.

## Description
For certain worfklows, when I try to view the subworkflow, I get an error page with the message: "Error: The workflow could not be found within the repository"

## Expected Behavior
I expect a rendering of the underlying tool/workflow.

## Actual Behavior
I get an error page with the message: "Error: The workflow could not be found within the repository"

## Steps to Reproduce
1. go to https://view.commonwl.org/workflows/github.com/ICGC-TCGA-PanCancer/OxoG-Dockstore-Tools/blob/develop/annotator_sub_wf.cwl
2. Double-click on the step that calls the subworkflow named "level_0"
3. You will get the message: "Error: The workflow could not be found within the repository"

This also happens for the "qa_check" subworkflow.
1. got to https://view.commonwl.org/workflows/github.com/ICGC-TCGA-PanCancer/OxoG-Dockstore-Tools/blob/develop/oxog_varbam_annotate_wf.cwl
2. double-click "qa_check"
3. Get error message.

Interesting to note is that the qa_check workflow renders if you load it separately:

https://view.commonwl.org/workflows/github.com/ICGC-TCGA-PanCancer/OxoG-Dockstore-Tools/blob/develop/qa_check_subwf.cwl

## Context
Trying to show diagrams to new users who are using the workflow and trying to use the diagrams to help understand it.

## Your Environment
Browser is Vivaldi 1.12.955.36, based on Chrome 61.