Use Error instead of literal for promise rejection

src/plugins/syncPlay/core/Helper.js

@@ -26,7 +26,7 @@ export function waitForEventOnce(emitter, eventType, timeout, rejectEventTypes)
         let rejectTimeout;
         if (timeout) {
             rejectTimeout = setTimeout(() => {
-                reject('Timed out.');
+                reject(new Error('Timed out.'));
             }, timeout);
         }
 

src/plugins/syncPlay/core/QueueCore.js

@@ -123,7 +123,7 @@ class QueueCore {
 
         if (!itemIds.length) {
             if (this.lastPlayQueueUpdate && playQueueUpdate.LastUpdate.getTime() <= this.getLastUpdateTime()) {
-                return Promise.reject('Trying to apply old update');
+                return Promise.reject(new Error('Trying to apply old update'));
             }
 
             this.lastPlayQueueUpdate = playQueueUpdate;

src/plugins/syncPlay/core/timeSync/TimeSync.js

@@ -113,7 +113,7 @@ class TimeSync {
      */
     requestPing() {
         console.warn('SyncPlay TimeSync requestPing: override this method!');
-        return Promise.reject('Not implemented.');
+        return Promise.reject(new Error('Not implemented.'));
     }
 
     /**