src/vs/workbench/contrib/debug/common/debugModel.ts/Thread/getTopStackFrame
class Thread:	getTopStackFrame(): IStackFrame | undefined {
		const callStack = this.getCallStack();
		// Allow stack frame without source and with instructionReferencePointer as top stack frame when using disassembly view.
		const firstAvailableStackFrame = callStack.find(sf => !!(sf &&
			((this.stoppedDetails?.reason === 'instruction breakpoint' || (this.stoppedDetails?.reason === 'step' && this.lastSteppingGranularity === 'instruction')) && sf.instructionPointerReference) ||
			(sf.source && sf.source.available && sf.source.presentationHint !== 'deemphasize')));
		return firstAvailableStackFrame || (callStack.length > 0 ? callStack[0] : undefined);
	}