Layers - Prevent brushes from going null when provider is missing

Layers - Set broken state when brush provider is missing
UI - Tweaked broken state visuals

src/Artemis.UI.Shared/Services/ProfileEditor/Commands/ChangeLayerBrush.cs

@@ -54,7 +54,8 @@ public class ChangeLayerBrush : IProfileEditorCommand, IDisposable
     /// <inheritdoc />
     public void Undo()
     {
-        _layer.ChangeLayerBrush(_previousBrush);
+        if (_previousBrush != null)
+            _layer.ChangeLayerBrush(_previousBrush);
         _executed = false;
     }
 

src/Artemis.UI.Shared/Styles/Artemis.axaml

@@ -21,6 +21,7 @@
 
     <!-- Custom styles -->
     <StyleInclude Source="/Styles/Border.axaml" />
+    <StyleInclude Source="/Styles/BrokenState.axaml" />
     <StyleInclude Source="/Styles/Skeleton.axaml" />
     <StyleInclude Source="/Styles/Button.axaml" />
     <StyleInclude Source="/Styles/Condensed.axaml" />

src/Artemis.UI.Shared/Styles/BrokenState.axaml

@@ -0,0 +1,20 @@
+<Styles xmlns="https://github.com/avaloniaui"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:controls="clr-namespace:FluentAvalonia.UI.Controls;assembly=FluentAvalonia"
+        xmlns:avalonia="clr-namespace:Material.Icons.Avalonia;assembly=Material.Icons.Avalonia">
+    <Design.PreviewWith>
+
+        <controls:HyperlinkButton Grid.Column="0" Classes="icon-button icon-button-small broken-state-button" Margin="50">
+            <avalonia:MaterialIcon Kind="AlertCircle" />
+        </controls:HyperlinkButton>
+    </Design.PreviewWith>
+
+    <!-- Add Styles Here -->
+    <Style Selector="controls|HyperlinkButton.broken-state-button avalonia|MaterialIcon">
+        <Setter Property="Foreground" Value="#E74C4C" />
+    </Style>
+
+    <Style Selector="controls|HyperlinkButton.broken-state-button:pointerover avalonia|MaterialIcon">
+        <Setter Property="Foreground" Value="#B93F3F" />
+    </Style>
+</Styles>