Abstract TypeScript methods do not work

Describe the bug

When extending an abstract class with an abstract method, the pxt build fails.

To Reproduce

Run pxt build for the program below.

abstract class AbstractPlayer {
    abstract play(): void
}

class Player extends AbstractPlayer {
    play(): void {
        music.play(music.tonePlayable(262, music.beat(BeatFraction.Whole)), music.PlaybackMode.UntilDone)
    }
}

const player = new Player()
player.play()

The compilation fails with

INTERNAL ERROR: Error: Assertion failed
    at Object.assert (/Users/pavel/Git/Microbit/makecode/node_modules/pxt-core/built/pxt.js:98695:27)
    at getVTable (/Users/pavel/Git/Microbit/makecode/node_modules/pxt-core/built/pxt.js:133474:32)
    at emitVTables (/Users/pavel/Git/Microbit/makecode/node_modules/pxt-core/built/pxt.js:134517:21)
    at Object.compileBinary (/Users/pavel/Git/Microbit/makecode/node_modules/pxt-core/built/pxt.js:133162:13)
    at Object.compile (/Users/pavel/Git/Microbit/makecode/node_modules/pxt-core/built/pxt.js:137199:40)
    at /Users/pavel/Git/Microbit/makecode/node_modules/pxt-core/built/pxt.js:165353:21
make: *** [build] Error 20

When changing the AbstractPlayer to

abstract class AbstractPlayer {
    play(): void {}
}

The compilation succeeds and the code works well on micro:bit.

Expected behavior
The compilation should succeed.

Desktop (please complete the following information):

• OS: macOS Sequoia 15.1.1
• target: v7.1.15
• pxt-core v11.3.3

Reproduce the failure with the abstract TypeScript example by running pxt build on the micro:bit target. Start from the reported getVTable and emitVTables paths in pxt-core/built/pxt.js, then compare them with the successful concrete-method variant. Done means the abstract-method program compiles and runs without the assertion failure.