Don't count missing annotation values as changed if empty string passed

Similar to 0d377a1c4a, this fixes an unnecessary annotation reload and
loss of unsaved typing on auto-sync immediately after an annotation is
created.

chrome/content/zotero/xpcom/data/item.js

@@ -3671,6 +3671,14 @@ for (let name of ['type', 'text', 'comment', 'color', 'pageLabel', 'sortIndex',
 		set: function (value) {
 			this._requireData('annotation');
 			
+			// Normalize values
+			if (typeof value == 'string') {
+				value = value.trim().normalize();
+				if (value === "") {
+					value = null;
+				}
+			}
+			
 			if (this._getLatestField(field) === value) {
 				return;
 			}

test/content/support.js

@@ -942,7 +942,12 @@ async function createAnnotation(type, parentItem, options = {}) {
 	if (type == 'highlight') {
 		annotation.annotationText = Zotero.Utilities.randomString();
 	}
-	annotation.annotationComment = Zotero.Utilities.randomString();
+	if (options.comment !== undefined) {
+		annotation.annotationComment = options.comment;
+	}
+	else {
+		annotation.annotationComment = Zotero.Utilities.randomString();
+	}
 	annotation.annotationColor = '#ffd400';
 	var page = Zotero.Utilities.rand(1, 100);
 	annotation.annotationPageLabel = `${page}`;

test/tests/itemTest.js

@@ -1333,6 +1333,20 @@ describe("Zotero.Item", function () {
 			});
 		});
 		
+		describe("#annotationComment", function () {
+			it("should not mark object without comment as changed if empty string", async function () {
+				var annotation = await createAnnotation('highlight', attachment, { comment: "" });
+				annotation.annotationComment = "";
+				assert.isFalse(annotation.hasChanged());
+			});
+			
+			it("should clear existing value when empty string is passed", async function () {
+				var annotation = await createAnnotation('highlight', attachment);
+				annotation.annotationComment = "";
+				assert.isTrue(annotation.hasChanged());
+			});
+		});
+		
 		describe("#saveTx()", function () {
 			it("should save a highlight annotation", async function () {
 				var annotation = new Zotero.Item('annotation');