[python] Fix python vector syntax issue

[tobil4sk]

The test for this issue was generating a python syntax warning in our CI:
https://github.com/HaxeFoundation/haxe/blob/development/tests/unit/src/unit/issues/Issue4986.hx

bin/unit.py:72732: SyntaxWarning: 'int' object is not subscriptable; perhaps you missed a comma?

Can be simplified down to this example:

(new haxe.ds.Vector(1))[0];

This was generating the following python code:

[None]*1[0] # it thinks we are trying to index the 1

Now Haxe correctly generates this python code:

([None]*1)[0] # indexing the array

(Side note: there is also a syntax warning for None(1) elsewhere, but I think this probably isn't that important, since calling null is what the test does anyway)