Don't trigger 'redraw' event on attachment download 404

There's no need to refresh the attachments column of the item row if
nothing was downloaded.

Also remove some unnecessary logging

chrome/content/zotero/xpcom/storage/storageRequest.js

@@ -56,6 +56,7 @@ Zotero.Sync.Storage.Request = function (options) {
 	this._deferred = Zotero.Promise.defer();
 	this._running = false;
 	this._stopping = false;
+	this._progressUpdated = false;
 	this._percentage = 0;
 	this._remaining = null;
 	this._maxSize = null;
@@ -199,7 +200,6 @@ Zotero.Sync.Storage.Request.prototype.start = Zotero.Promise.coroutine(function*
 		result.updateFromResults(results);
 		
 		Zotero.debug(this.Type + " request " + this.name + " finished");
-		Zotero.debug(result + "");
 		
 		return result;
 	}
@@ -211,7 +211,11 @@ Zotero.Sync.Storage.Request.prototype.start = Zotero.Promise.coroutine(function*
 		this._finished = true;
 		this._running = false;
 		
-		Zotero.Sync.Storage.setItemDownloadPercentage(this.name, false);
+		// Clear the progress bar if it was set previously or we were told not to
+		// (e.g., by zfs.js on a 404)
+		if (this._progressUpdated || !this.skipProgressBarUpdate) {
+			Zotero.Sync.Storage.setItemDownloadPercentage(this.name, false);
+		}
 		
 		if (this._onStop) {
 			this._onStop.forEach(x => x());
@@ -258,7 +262,7 @@ Zotero.Sync.Storage.Request.prototype.onProgress = function (progress, progressM
 		return;
 	}
 	
-	if (progressMax != this.progressMax) {
+	if (this.progressMax && progressMax != this.progressMax) {
 		Zotero.debug("progressMax has changed from " + this.progressMax
 			+ " to " + progressMax + " for request '" + this.name + "'", 2);
 	}
@@ -267,7 +271,12 @@ Zotero.Sync.Storage.Request.prototype.onProgress = function (progress, progressM
 	this.progressMax = progressMax;
 	
 	if (this.type == 'download') {
-		Zotero.Sync.Storage.setItemDownloadPercentage(this.name, this.percentage);
+		// Update progress bar if we didn't skip to 100 on the first step (which might indicate a
+		// request failure)
+		if (this._progressUpdated || progress != progressMax) {
+			Zotero.Sync.Storage.setItemDownloadPercentage(this.name, this.percentage);
+			this._progressUpdated = true;
+		}
 	}
 	
 	if (this._onProgress) {

chrome/content/zotero/xpcom/storage/zfs.js

@@ -154,6 +154,8 @@ Zotero.Sync.Storage.Mode.ZFS.prototype = {
 					if (status != 200) {
 						if (status == 404) {
 							Zotero.debug("Remote file not found for item " + item.libraryKey);
+							// Don't refresh item pane rows when nothing happened
+							request.skipProgressBarUpdate = true;
 							deferred.resolve(new Zotero.Sync.Storage.Result);
 							return;
 						}