Anim save issues with palette and blank frames

[mriale]

With the changes made for saving flattened layers in issue #151, I introduced these problems:

• blank frames
• garbled palettes

Steps to reproduce blank frames:

• load an animation like this one:
  
• save the animation as IFF ANIM
• load it back in again
• the result will have blank frames after the first one

Steps to reproduce garbled palettes:

• load the above animation
• hold down the 2 key to loop through the entire animation
• save the animation as IFF ANIM
• load it back in again
• the result will have garbled colors on some frames

Another issue I also see is that there is a border on the right of the ANIM that is not in original GIF.

[mriale]

Fixed all of the above issues.