define max size for legend

pdb-js/src/app/plot-view/plot-view.component.html

@@ -1,7 +1,7 @@
 
 <!---->
 <div cdkDrag 
-    [ngClass]="{'hidden': !imageUrl || showStats}" 
+    [ngClass]="{'hidden': !imageUrl || showStats || dataSeries().length == 0}" 
     class="plot-view--legend" 
     [cdkDragFreeDragPosition]="legendInitialPosition">
   <div cdkDragHandle></div>

pdb-js/src/app/plot-view/plot-view.component.scss

@@ -36,6 +36,9 @@ img {
               0 2px 2px 0 rgba(0, 0, 0, 0.14),
               0 1px 5px 0 rgba(0, 0, 0, 0.12);
   background-color: white;
+  max-height: 30em;
+  overflow: auto;
+  max-width: 60em;
 }
 
 .plot-view--legend:active {
@@ -46,6 +49,7 @@ img {
 .plot-view--legend div[cdkDragHandle] {
   visibility: hidden;
   height: 1.2rem;
+  flex-shrink: 0;
 }
 
 .plot-view--legend:hover div[cdkDragHandle] {