Fix indexing into objects with non-slice things

[daboross]

This allows the following Python code to compile and work:

obj = {"a": "hello"}
print(obj["a"])

This was previously compiled to:

export var obj=dict([["a","hello"]]);
print();

With this PR, it will now be compiled to:

export var obj=dict([["a","hello"]]);
print(obj["a"]);