Issue handling sweep bits in to_crumble_url function

[AlexBourassa]

Here is an example of the issue. If you do

stim.Circuit("""
QUBIT_COORDS(0, 5) 0
QUBIT_COORDS(1, 4) 1
QUBIT_COORDS(1, 5) 2
CX sweep[0] 0 sweep[1] 1 sweep[2] 2
M 0 1 2
""").to_crumble_url()

The circuit that shows up when you open the link is

QUBIT_COORDS(0, 5) 0
QUBIT_COORDS(1, 4) 1
QUBIT_COORDS(1, 5) 2
CX 0 0
TICK
CX 0 1
TICK
CX 0 2
TICK