Fixes "Cannot read property 'collection' of null" when distance is a disabled element is moved

Author: Szabolcs Szoke

src/Manager.js

@@ -20,6 +20,10 @@ export default class Manager {
     }
   }
 
+  isActive() {
+    return this.active;
+  }
+
   getActive() {
     return find(
       this.refs[this.active.collection],

src/SortableContainer/index.js

@@ -205,7 +205,7 @@ export default function sortableContainer(WrappedComponent, config = {withRef: f
         if (!distance && (!pressThreshold || pressThreshold && delta >= pressThreshold)) {
           clearTimeout(this.cancelTimer);
           this.cancelTimer = setTimeout(this.cancel, 0);
-        } else if (distance && delta >= distance) {
+        } else if (distance && delta >= distance && this.manager.isActive()) {
           this.handlePress(e);
         }
       }