move Bk2 -> TasMovie conversion logic from Tastudio to MovieSession, fix crashing when loading .bk2 movies from the tastudio menu

BizHawk.Client.Common/movie/MovieSession.cs

@@ -1,7 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
-
+using BizHawk.Client.Common.MovieConversionExtensions;
 using BizHawk.Emulation.Common;
 using BizHawk.Emulation.Cores.Nintendo.Gameboy;
 
@@ -355,6 +355,14 @@ namespace BizHawk.Client.Common
 			Movie = MovieService.DefaultInstance;
 		}
 
+		public void ConvertToTasProj()
+		{
+			Movie.Save();
+			Movie = Movie.ToTasMovie();
+			Movie.Save();
+			Movie.SwitchToPlay();
+		}
+
 		private void ClearFrame()
 		{
 			if (Movie.IsPlaying())

BizHawk.Client.Common/movie/interfaces/IMovieSession.cs

@@ -64,5 +64,10 @@ namespace BizHawk.Client.Common
 		void ToggleMultitrack();
 
 		void StopMovie(bool saveChanges = true);
+
+		/// <summary>
+		/// If a movie is active, it will be converted to a <see cref="TasMovie" />
+		/// </summary>
+		void ConvertToTasProj();
 	}
 }

BizHawk.Client.EmuHawk/MainForm.Movie.cs

@@ -1,4 +1,5 @@
-using System.Windows.Forms;
+using System;
+using System.Windows.Forms;
 
 using BizHawk.Client.Common;
 using BizHawk.Emulation.Common;
@@ -9,6 +10,11 @@ namespace BizHawk.Client.EmuHawk
 	{
 		public bool StartNewMovie(IMovie movie, bool record)
 		{
+			if (movie == null)
+			{
+				throw new ArgumentNullException($"{nameof(movie)} cannot be null.");
+			}
+
 			try
 			{
 				MovieSession.QueueNewMovie(movie, record, Emulator);

BizHawk.Client.EmuHawk/tools/TAStudio/TAStudio.MenuItems.cs

@@ -121,10 +121,12 @@ namespace BizHawk.Client.EmuHawk
 					else if (ofd.FileName.EndsWith(Bk2Movie.Extension))
 					{
 						var result1 = MessageBox.Show("This is a regular movie, a new project must be created from it, in order to use in TAStudio\nProceed?", "Convert movie", MessageBoxButtons.OKCancel, MessageBoxIcon.Question);
-						if (result1 == DialogResult.OK)
+						if (result1.IsOk())
 						{
+							_initializing = true; // Starting a new movie causes a core reboot
 							MainForm.StartNewMovie(MovieService.Get(ofd.FileName), false);
 							ConvertCurrentMovieToTasproj();
+							_initialized = false;
 							StartNewMovieWrapper(false);
 							SetUpColumns();
 							SetTextProperty();

BizHawk.Client.EmuHawk/tools/TAStudio/TAStudio.cs

@@ -615,11 +615,9 @@ namespace BizHawk.Client.EmuHawk
 
 		private void ConvertCurrentMovieToTasproj()
 		{
-			MovieSession.Movie.Save();
-			MovieSession.Movie = MovieSession.Movie.ToTasMovie();
-			MovieSession.Movie.Save();
-			MovieSession.Movie.SwitchToPlay();
+			MovieSession.ConvertToTasProj();
 			Settings.RecentTas.Add(MovieSession.Movie.Filename);
+			MainForm.SetMainformMovieInfo();
 		}
 
 		private bool LoadFile(FileInfo file, bool startsFromSavestate = false, int gotoFrame = 0)