Fix exception on opening Play Movie dialog with multiple movies

fixes 9211007a1

src/BizHawk.Client.EmuHawk/movie/PlayMovie.cs

@@ -195,18 +195,25 @@ namespace BizHawk.Client.EmuHawk
 			}
 
 			// Prefer tas files
+			// but `_movieList` should only contain `.bk2` and `.tasproj` so... isn't that all of them? or, it is now I've fixed the case-sensitivity bug --yoshi
 			var tas = new List<int>();
 			for (var i = 0; i < indices.Count; i++)
 			{
 				foreach (var ext in MovieService.MovieExtensions)
 				{
-					if (Path.GetExtension(_movieList[indices[i]].Filename)?.ToUpper() == $".{ext}")
+					if ($".{ext}".Equals(Path.GetExtension(_movieList[indices[i]].Filename), StringComparison.InvariantCultureIgnoreCase))
 					{
 						tas.Add(i);
 					}
 				}
 			}
 
+			if (tas.Count is 0)
+			{
+				if (_movieList.Count is not 0) HighlightMovie(0);
+				return;
+			}
+
 			if (tas.Count == 1)
 			{
 				HighlightMovie(tas[0]);