Absent datSet in GSEControl causes console error in Message Binding subscriber plugin

[danyill]

Describe the bug

While looking at #1261, I realise that the message binding plugins are not robust for a GSEControl (and probably a SampledValueControl) with a missing datSet which we assume to be present.

open-scd/src/editors/subscription/goose/subscriber-list.ts

Lines 197 to 227 in a238cc9

	private async onGooseSubscriptionEvent(event: GooseSubscriptionEvent) {
	let iedToSubscribe = event.detail.element;
	if (view == View.SUBSCRIBER) {
	const dataSetName = event.detail.element.getAttribute('datSet');
	this.currentUsedDataset =
	event.detail.element.parentElement?.querySelector(
	`DataSet[name="${dataSetName}"]`
	);
	this.currentSelectedGseControl = event.detail.element;
	this.currentGooseIedName = event.detail.element
	.closest('IED')
	?.getAttribute('name');
	iedToSubscribe = this.currentSelectedIed!;
	}
	switch (event.detail.subscribeStatus) {
	case SubscribeStatus.Full: {
	this.unsubscribe(iedToSubscribe);
	break;
	}
	case SubscribeStatus.Partial: {
	this.subscribe(iedToSubscribe);
	break;
	}
	case SubscribeStatus.None: {
	this.subscribe(iedToSubscribe);
	break;
	}
	}
	}

To Reproduce

Steps to reproduce the behavior:

1. Use the test file, test/testfiles/editors/MessageBindingGOOSE2007B4.scd
2. Open the Message Binding (GOOSE) plugin
3. Select the Subscriber view.
4. Select IED 3.
5. Try to connect GCB2 (IED 4)

Observe a console log:

Expected behavior

A subscription which does not succeed should not cause a console error.

An absent datSet is allowed according to the standard:

The name of the data set to be sent by the GSE control block. For type=GSSE, the
FCDA definitions in this data set shall be interpreted as DataLabels according to
IEC 61850-7-2. The attribute datSet should only be missing within an ICD-File, or to
indicate an unused control block. It resides in LLN0 like the control block

We should probably filter out control blocks which don't have a datSet attribute before building the lists.

[danyill]

This also causes glitches when subscribing/unsubscribing

There is a similar issue in the publisher view -- we shouldn't show control blocks unless they are linked to a DataSet