Extra safety checks on mod file conversions.

Author: Lunaretic

xivModdingFramework/Models/FileTypes/Mdl.cs

@@ -4431,9 +4431,15 @@ public async Task<long> CopyModel(string originalPath, string newPath, string so
             var xMdl = await GetRawMdlData(originalPath, false, offset);
             var model = TTModel.FromRaw(xMdl);
 
+            if (model == null)
+            {
+                throw new InvalidDataException("Source model file does not exist.");
+            }
+
             var originalRace = IOUtil.GetRaceFromPath(originalPath);
             var newRace = IOUtil.GetRaceFromPath(newPath);
 
+
             if(originalRace != newRace)
             {
                 // Convert the model to the new race.