JavaScript Errors in SwaggerHub Editor

My (previously working) 3.0 specifications are now reporting JavaScript errors in the SwaggerHub editor. It does correctly render the documentation view, but it reports that the specification has errors, which also show up in the browser's console log. I've crafted an artificial example that shows the same problem and I've attached it.

 

In Error list:

"Cannot read property '1' of undefined"

 

In console log:

main-bde26d4f53c20f5fd7ebd6f6e0601ff3.js:104 TypeError: Cannot read property '1' of undefined
at o (main-bde26d4f53c20f5fd7ebd6f6e0601ff3.js:106)
at Object.i [as applyPatch] (main-bde26d4f53c20f5fd7ebd6f6e0601ff3.js:106)
at Object.o [as applyPatch] (main-bde26d4f53c20f5fd7ebd6f6e0601ff3.js:104)
at e.value (main-bde26d4f53c20f5fd7ebd6f6e0601ff3.js:104)
at main-bde26d4f53c20f5fd7ebd6f6e0601ff3.js:104
at Array.forEach (<anonymous>)
at e.value (main-bde26d4f53c20f5fd7ebd6f6e0601ff3.js:104)
at e (main-bde26d4f53c20f5fd7ebd6f6e0601ff3.js:104)
at main-bde26d4f53c20f5fd7ebd6f6e0601ff3.js:104
at e.value (main-bde26d4f53c20f5fd7ebd6f6e0601ff3.js:104)