Override `isHidden` in converse-minimize

Otherwise `isHidden` might return true because `minimized` is set to
`true` but `converse-minimize` is not enabled.

src/converse-minimize.js

@@ -71,6 +71,10 @@ converse.plugins.add('converse-minimize', {
                     return this;
                 }
                 return this.__super__.maybeShow.apply(this, arguments);
+            },
+
+            isHidden () {
+                return this.__super__.isHidden.call(this) || this.get('minimized');
             }
         },
 

src/headless/converse-chat.js

@@ -1142,10 +1142,8 @@ converse.plugins.add('converse-chat', {
              * @returns {boolean}
              */
             isHidden () {
-                return this.get('hidden') ||
-                    this.get('minimized') ||
-                    this.isScrolledUp() ||
-                    _converse.windowState === 'hidden';
+                // Note: This methods gets overridden by converse-minimize
+                return this.get('hidden') || this.isScrolledUp() || _converse.windowState === 'hidden';
             },
 
             /**