Remove args indexing from vae decoding

Newer versions of python support indexing multiple dimensions by
prefixing a variable with an aseterisk similar to how it can be used for
functions. This was utilized to discard higher dimensions (excess
frames) produced by vae output when using temporal vae, but causes
syntax errors with older versions of python. This is fixed by using a
while loop instead.

Resolves #321

videohelpersuite/nodes.py

@@ -287,7 +287,8 @@ class VideoCombine:
             #repush first_image
             images = itertools.chain([first_image], images)
             #A single image has 3 dimensions. Discard higher dimensions
-            first_image = first_image[*([0]*(len(first_image.shape)-3))]
+            while len(first_image.shape) > 3:
+                first_image = first_image[0]
         else:
             first_image = images[0]
             images = iter(images)