🍏 Fix bottom bar disappearing on apple os when it's single asset mode.

Author: AlexV525

lib/src/widget/asset_picker.dart

@@ -1018,7 +1018,7 @@ class AssetPicker extends StatelessWidget {
                             child: Stack(
                               children: <Widget>[
                                 Positioned.fill(child: assetsGrid(context)),
-                                if (!isSingleAssetMode)
+                                if (!isSingleAssetMode || isAppleOS)
                                   PositionedDirectional(
                                     bottom: 0.0,
                                     child: bottomActionBar(context),