ImportMapAcresAll: update CopyTo index to 0 (#245)

The second parameter of `Array.CopyTo` takes an integer that represents the index in array at which copying begins. Therefore in this case it should be set to 0 instead of the array's length.

NHSE.WinForms/Subforms/Map/MapDumpHelper.cs

@@ -245,8 +245,8 @@ public static bool ImportMapAcresAll(byte[] data)
                 return false;
             }
 
-            modified.CopyTo(data, modified.Length);
+            modified.CopyTo(data, 0);
             return true;
         }
     }
-}
+}