chore: update theme.xaml

Author: NaBian

src/Net_40/HandyControl_Net_40/Themes/Theme.xaml

@@ -1186,7 +1186,7 @@
 			</Grid.RowDefinitions>
 			<AdornedElementPlaceholder x:Name="adornedElementPlaceholder" />
 			<hc:TransitioningContentControl TransitionMode="Top2Bottom" Grid.Row="1" ClipToBounds="True">
-				<TextBlock Foreground="{DynamicResource DangerBrush}" Margin="2,2,0,0" Text="{Binding Path=AdornedElement.(Validation.Errors)[0].ErrorContent, ElementName=adornedElementPlaceholder}" />
+				<TextBlock Foreground="{DynamicResource DangerBrush}" Margin="2,2,0,0" Text="{Binding Path=AdornedElement.(Validation.Errors)/ErrorContent, ElementName=adornedElementPlaceholder}" />
 			</hc:TransitioningContentControl>
 		</Grid>
 	</ControlTemplate>

src/Shared/HandyControl_Shared/Themes/Theme.xaml

@@ -1186,7 +1186,7 @@
 			</Grid.RowDefinitions>
 			<AdornedElementPlaceholder x:Name="adornedElementPlaceholder" />
 			<hc:TransitioningContentControl TransitionMode="Top2Bottom" Grid.Row="1" ClipToBounds="True">
-				<TextBlock Foreground="{DynamicResource DangerBrush}" Margin="2,2,0,0" Text="{Binding Path=AdornedElement.(Validation.Errors)[0].ErrorContent, ElementName=adornedElementPlaceholder}" />
+				<TextBlock Foreground="{DynamicResource DangerBrush}" Margin="2,2,0,0" Text="{Binding Path=AdornedElement.(Validation.Errors)/ErrorContent, ElementName=adornedElementPlaceholder}" />
 			</hc:TransitioningContentControl>
 		</Grid>
 	</ControlTemplate>