Don't preserve height when clear_output(wait=False) is called

IPython/html/static/notebook/js/outputarea.js

@@ -625,11 +625,14 b' var IPython = (function (IPython) {'
 
             this.clear_queued = true;
         } else {
-            this.clear_queued = false;
 
-            // Fix the output div's height
+            // Fix the output div's height if the clear_output is waiting for
+            // new output (it is being used in an animation).
+            if (this.clear_queued) {
             var height = this.element.height();
             this.element.height(height);
+                this.clear_queued = false;
+            }
 
             // clear all, no need for logic
             this.element.html("");