Fix NRE

JimBobSquarePants · JimBobSquarePants · commit 73067b974259 · 2023-05-15T22:52:41.000+10:00
diff --git a/src/ImageSharp/Formats/Gif/GifEncoderCore.cs b/src/ImageSharp/Formats/Gif/GifEncoderCore.cs
@@ -560,6 +560,7 @@ private void WriteGraphicalControlExtension(GifFrameMetadata? metadata, int tran
         bool hasTransparency;
         if (metadata is null)
         {
+            metadata = new();
             hasTransparency = transparencyIndex > -1;
         }
         else

Original file line number	Diff line number	Diff line change
`@@ -560,6 +560,7 @@ private void WriteGraphicalControlExtension(GifFrameMetadata? metadata, int tran`
`560`	`560`	`bool hasTransparency;`
`561`	`561`	`if (metadata is null)`
`562`	`562`	`{`
	`563`	`+ metadata = new();`
`563`	`564`	`hasTransparency = transparencyIndex > -1;`
`564`	`565`	`}`
`565`	`566`	`else`