fix(get-selector): don't throw error for disconnected fragment (#1802)

* fix(get-selector): don't throw error for disconnected fragement

* skip phantom

* fix test

Author: straker

lib/core/utils/get-selector.js

@@ -392,6 +392,9 @@ axe.utils.getSelector = function createUniqueSelector(elm, options = {}) {
 		// DOCUMENT_FRAGMENT
 		let stack = [];
 		while (doc.nodeType === 11) {
+			if (!doc.host) {
+				return '';
+			}
 			stack.push({ elm: elm, doc: doc });
 			elm = doc.host;
 			doc = elm.getRootNode();

test/core/utils/get-selector.js

@@ -593,4 +593,14 @@ describe('axe.utils.getSelector', function() {
 		var test = document.querySelector(sel);
 		assert.isTrue(test === top);
 	});
+
+	it('should not error if fragment is no longer in the DOM', function() {
+		var fragment = document.createDocumentFragment();
+		var node = document.createElement('div');
+		fragment.appendChild(node);
+		fixtureSetup();
+		assert.doesNotThrow(function() {
+			axe.utils.getSelector(node);
+		});
+	});
 });