CmdPal: Prevent scaling empty icon size (#49385)

## Summary of the Pull Request

This PR prevents a crash caused by attempting to apply DPI scaling to an
empty icon. Size.Empty has width and height values of negative infinity.
Scaling those values still produces negative infinity, which is not
valid for a Size.

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## PR Checklist

- [x] Closes: #49360
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issues) -->
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

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or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

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wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

src/modules/cmdpal/Microsoft.CmdPal.UI/Helpers/Icons/IconLoaderService.cs

@@ -155,7 +155,9 @@ internal sealed partial class IconLoaderService : IIconLoaderService
         Size iconSize,
         double scale)
     {
-        var scaledSize = new Size(iconSize.Width * scale, iconSize.Height * scale);
+        var scaledSize = iconSize.IsEmpty
+            ? iconSize
+            : new Size(iconSize.Width * scale, iconSize.Height * scale);
 
         if (!string.IsNullOrEmpty(iconString))
         {
@@ -215,7 +217,9 @@ internal sealed partial class IconLoaderService : IIconLoaderService
 
     private static IconSource? GetStringIconSource(string iconString, string? fontFamily, Size size)
     {
-        var iconSize = (int)Math.Max(size.Width, size.Height);
+        var iconSize = size.IsEmpty
+            ? DefaultIconSize
+            : (int)Math.Max(size.Width, size.Height);
         return IconPathConverter.IconSourceMUX(iconString, fontFamily, iconSize);
     }
 }

src/modules/cmdpal/Microsoft.CmdPal.UI/Helpers/Icons/IconProvider.cs

@@ -2,6 +2,7 @@
 // The Microsoft Corporation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using ManagedCommon;
 using Microsoft.CmdPal.UI.Controls;
 using Microsoft.CmdPal.UI.ViewModels;
 using Microsoft.Extensions.DependencyInjection;
@@ -61,6 +62,11 @@ public static partial class IconProvider
                 _ => null,
             };
         }
+        catch (Exception ex)
+        {
+            Logger.LogError("Failed to provide icon source", ex);
+            args.Value = null;
+        }
         finally
         {
             deferral.Complete();