Fix warnings from nullabilty

LinearExecutable/ImportModuleNameTableEntry.cs

@@ -36,6 +36,10 @@ namespace SabreTools.Models.LinearExecutable
         /// This is a variable length string with it's length defined in bytes by
         /// the LEN field. The string is case sensitive and is not null terminated.
         /// </remarks>
+#if NET48
         public string Name;
+#else
+        public string? Name;
+#endif
     }
 }