Added missing check for the number of bytes that were read.

Author: dlemstra

src/Magick.NET/ImageOptimizers/ImageOptimizerHelper.cs

@@ -106,9 +106,9 @@ public static void CheckStream(Stream stream)
     private static IMagickFormatInfo? GetFormatInformationFromHeader(Stream stream)
     {
         var buffer = new byte[4];
-        stream.Read(buffer, 0, buffer.Length);
+        var count = stream.Read(buffer, 0, buffer.Length);
 
-        if (buffer[0] == 0 && buffer[1] == 0 && buffer[2] == 1 && buffer[3] == 0)
+        if (count == buffer.Length && buffer[0] == 0 && buffer[1] == 0 && buffer[2] == 1 && buffer[3] == 0)
             return MagickFormatInfo.Create(MagickFormat.Ico);
 
         return null;