do not log in clearPromiseQueue is _promises is empty

Author: etpinard

src/plot_api/plot_api.js

@@ -353,7 +353,10 @@ function getGraphDiv(gd) {
 
 // clear the promise queue if one of them got rejected
 function clearPromiseQueue(gd) {
-    Lib.log('Clearing previous rejected promises from queue.');
+    if(Array.isArray(gd._promises) && gd._promises.length > 0) {
+        Lib.log('Clearing previous rejected promises from queue.');
+    }
+
     gd._promises = [];
 }