Two big things here.
1) I don't think movieCollection.add("${movie1}"); will work because I don't think EL works inside of scriptlets.
2) <myTags:movieTag movieList="${movieCollection}"> won't find your collection because your never added it to any scope. Try ending the scriptlet with a:
request.setAttribute("movieCollection", movieCollection);
Fixing this second part alone will solve the NullPointer.