drawer fix

Runtime/material/list_tile.cs

-using System;
 using System.Collections.Generic;
 using System.Linq;
 using Unity.UIWidgets.foundation;
         }
 
         void _mountChild(Widget widget, _ListTileSlot slot) {
-            Element oldChild = this.slotToChild[slot];
+            Element oldChild = this.slotToChild.ContainsKey(slot) ? this.slotToChild[slot] : null;
             Element newChild = this.updateChild(oldChild, widget, slot);
             if (oldChild != null) {
                 this.slotToChild.Remove(slot);

Runtime/service/system_chrome.cs

 
         public override int GetHashCode() {
             var hashCode = this.systemNavigationBarColor.GetHashCode();
-            hashCode = (hashCode * 397) ^ this.systemNavigationBarDividerColor.GetHashCode();
-            hashCode = (hashCode * 397) ^ this.statusBarColor.GetHashCode();
-            hashCode = (hashCode * 397) ^ this.statusBarBrightness.GetHashCode();
-            hashCode = (hashCode * 397) ^ this.statusBarIconBrightness.GetHashCode();
-            hashCode = (hashCode * 397) ^ this.systemNavigationBarIconBrightness.GetHashCode();
+            hashCode = (hashCode * 397) ^ (this.systemNavigationBarDividerColor != null
+                           ? this.systemNavigationBarDividerColor.GetHashCode()
+                           : 0);
+            hashCode = (hashCode * 397) ^ (this.statusBarColor != null ? this.statusBarColor.GetHashCode() : 0);
+            hashCode = (hashCode * 397) ^
+                       (this.statusBarBrightness != null ? this.statusBarBrightness.GetHashCode() : 0);
+            hashCode = (hashCode * 397) ^
+                       (this.statusBarIconBrightness != null ? this.statusBarIconBrightness.GetHashCode() : 0);
+            hashCode = (hashCode * 397) ^ (this.systemNavigationBarIconBrightness != null
+                           ? this.systemNavigationBarIconBrightness.GetHashCode()
+                           : 0);
             return hashCode;
         }
 

Samples/UIWidgetSample/MaterialSample.cs

                                 Scaffold.of(subContext).showSnackBar(new SnackBar(
                                     content: new Text("Float Alerting !")));
                             });
-                    })
+                    }),
+                drawer: new Drawer(
+                    child: new ListView(
+                        padding: EdgeInsets.zero,
+                        children: new List<Widget> {
+                            new ListTile(
+                                leading: new Icon(Unity.UIWidgets.material.Icons.account_circle),
+                                title: new Text("Login"),
+                                onTap: () => { }
+                            ),
+                            new Divider(
+                                height: 2.0f),
+                            new ListTile(
+                                leading: new Icon(Unity.UIWidgets.material.Icons.account_balance_wallet),
+                                title: new Text("Wallet"),
+                                onTap: () => { }
+                            ),
+                            new Divider(
+                                height: 2.0f),
+                            new ListTile(
+                                leading: new Icon(Unity.UIWidgets.material.Icons.accessibility),
+                                title: new Text("Balance"),
+                                onTap: () => { }
+                            )
+                        }
+                    )
+                )
+                
             );
         }
     }