fix isRecursiveCall failing on flyout blocks

[FurryR]

Resolves

Clicking "b" in the flyout will cause exceptions:

Uncaught TypeError: Cannot read properties of undefined (reading 'opcode')
    at n.isRecursiveCall (projects.bundle.js:2:4755076)
    at l.stepToProcedure (projects.bundle.js:2:4743915)
    at e.exports.startProcedure (projects.bundle.js:2:4691130)
    at e.exports.call (projects.bundle.js:2:4674841)
    at e.exports (projects.bundle.js:2:4712562)
    at l.stepThread (projects.bundle.js:2:4743130)
    at l.stepThreads (projects.bundle.js:2:4742334)
    at U._step (projects.bundle.js:2:4735971)
    at projects.bundle.js:2:4740977

Proposed Changes

Fixed the issue by adding flyoutBlocks as a fallback.
This patch was originally from TurboWarp#227.

Reason for Changes

I don't know. For better user experience?

Test Coverage

N/A