[Bug] merged pdb structure: any protein + DNA (1BNA.pdb) breaks Molecule3D

[IvoLeist]

Describe the bug
If I am trying to upload a merged pdb structure (any protein + DNA (1BNA.pdb)
Molecule3D stops working. This holds true for dash-bio on localhost and
https://dash-gallery.plotly.host/dash-molecule-3d-viewer/

To Reproduce

1. Download two pdb structures from rcsb.org (where one is a DNA duplex)
   (e.g. https://files.rcsb.org/download/1BNA.pdb and https://files.rcsb.org/download/2MRU.pdb)
2. Upload them in pymol (https://pymol.org/2/)
3. Save them in a new pdb file
4. Upload this file

Or download the attached example and change the file extension to .pdb
2mru_1bna_merged.txt

Expected behavior
It should show the two molecules

Bug message if hosted on local host
(This error originated from the built-in JavaScript code that runs Dash apps. Click to see the full stack trace or open your browser's console.)
TypeError: Cannot read property 'atom' of undefined

at u (http://localhost:8050/_dash-component-suites/dash_bio/async~moleculeviewer3.js?v=0.4.6&m=1579173631:1:264066)

at Object.drawCartoon (http://localhost:8050/_dash-component-suites/dash_bio/async~moleculeviewer3.js?v=0.4.6&m=1579173631:1:265971)

at e.globj (http://localhost:8050/_dash-component-suites/dash_bio/async~moleculeviewer3.js?v=0.4.6&m=1579173631:1:293822)

at $3Dmol.GLViewer.render (http://localhost:8050/_dash-component-suites/dash_bio/async~moleculeviewer3.js?v=0.4.6&m=1579173631:1:328877)

at t.value (http://localhost:8050/_dash-component-suites/dash_bio/async~moleculeviewer3.js?v=0.4.6&m=1579173631:1:5304)

at t.value (http://localhost:8050/_dash-component-suites/dash_bio/async~moleculeviewer3.js?v=0.4.6&m=1579173631:1:3633)

at commitLifeCycles (http://localhost:8050/_dash-component-suites/dash_renderer/[email protected]?v=1.1.2&m=1576595738:17484:22)

at commitAllLifeCycles (http://localhost:8050/_dash-component-suites/dash_renderer/[email protected]?v=1.1.2&m=1576595738:18871:7)

at HTMLUnknownElement.callCallback (http://localhost:8050/_dash-component-suites/dash_renderer/[email protected]?v=1.1.2&m=1576595738:143:14)

at Object.invokeGuardedCallbackDev (http://localhost:8050/_dash-component-suites/dash_renderer/[email protected]?v=1.1.2&m=1576595738:193:16)

[IvoLeist]

Below is the error showing up on
https://dash-gallery.plotly.host/dash-molecule-3d-viewer/

The number in front of Uncaught TypeError: Cannot read property 'children' of null
is constantly increasing + the app cannot be used any longer
(e.g. selecting a new molecule from the dropdown or uploading a new one.
*Page has to be reloaded to use it again