Editor: Don't use the BottomAppBar

The BottomAppBar has a SafeArea widget inside which seems to give it an
extra top padding on my phone (OnePlus), I'm not sure why it thinks this
extra top padding is required.

Maybe this workaround will fail on other devices

lib/editors/common.dart

@@ -133,9 +133,10 @@ class EditorBottomBar extends StatelessWidget {
       },
     );
 
-    return BottomAppBar(
+    return Container(
-      elevation: 0.0,
       color: Theme.of(context).scaffoldBackgroundColor,
+      child: SafeArea(
+        top: false,
         child: Row(
           children: <Widget>[
             Visibility(
@@ -160,6 +161,7 @@ class EditorBottomBar extends StatelessWidget {
           ],
           mainAxisAlignment: MainAxisAlignment.center,
         ),
+      ),
     );
   }
 }