variablesMap.changeVariableType does not remove empty maps which causes a crash when the workspace is cleared()

[stefan-stanca]

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Description

Reproduction steps

1. Create a workspace with a single variable of type "Int"
2. const variablesMap = workspace.current?.getVariableMap();
   variablesMap.changeVariableType(variable, "Bool");
3. workspace.current.clear();

Any workaround would be appreciated as it's currently blocking.

Priority

Blocker

Stack trace

react-dom.development.js:12056 Uncaught Error: Non-empty variable map
 at _Gb.clear (variable_map.ts:67:13)
 at _Ab.clear (workspace.ts:399:26)
 at _Ab.clear (workspace_svg.ts:2358:11)

Screenshots

No response

Browsers

No response

[gonfunko]

This was resolved in #9339, which is included in the latest Blockly v12.3.1. Updating to that version should take care of it, but please let us know/reopen this if not!