#1287 animated GIF rendering on zoom in

[Lars Friedrich]

INFO: freemind_version = 1.0.1; freemind_xml_version = 1.0.1
Build: 6

java_version = 1.8.0_211; os_name = Windows 10; os_version = 10.0

Steps to reproduce:
- Use "Insert -> Image" to insert an animated GIF file into a node.
- Use "Edit Long Node" to add width="100" and height="100" to the tag in order to set the scaling of the image
- Use "View -> Zoom in"

Result:
animated GIF is updated only in a subregion that has the given size (here: 100x100 pixels). The rest remains static.