JavaScript errors during blocks

Reported by another user:

```
Critical error
blockly_compressed.js:1239 Object {blank: Scheme, codeWorldLogo: Scheme, circle: Scheme, solidCircle: Scheme, thickCircle: Scheme…}
blockly_compressed.js:1239 Types do not match, when trying to type Program
blockly_compressed.js:1207 Uncaught TypeError: Cannot read property 'isTypeVar' of undefined
```

Start by reproducing the reported block interaction and inspect blockly_compressed.js at lines 1207 and 1239, where the type-mismatch and isTypeVar errors are logged. Trace the failing case from the reported block names and determine the conditions needed for the errors to stop.

Scritto dal modello di indicizzazione a partire dal testo della issue.