Incorrect binding with catalyze_complex macro on dimer substrate

[alubbock]

As reported by @acorbat on gitter, the catalyze_complex macro fails with a DanglingBondError in the following example, presumably due to the use of a dimer as a substrate:

from pysb import
from pysb.macros import

Model()

substrate = Monomer('S', ['bf', 'es'])
enzyme = Monomer('E', ['es'])
product = Monomer('P', ['bf'])

dimer = substrate(bf=1, es=None) % substrate(bf=1, es=None)

catalyze_complex(enzyme, 'es', dimer, 'es', product(bf=None), [1e-6, 1e-3, 1], m2=substrate(bf=1, es=None))

The macro attempts to produce the following to rules (if the error is suppressed):

Rule('bind_SS_E', S(bf=1, es=None) % S(bf=1, es=None) + E(es=None) | S(bf=1, es=50) % S(bf=1, es=None) % E(es=50), bind_SS_E_kf, bind_SS_E_kr)
Rule('catalyze_ESS_to_E_P', E(es=1) % S(bf=1, es=50) % S(bf=1, es=None) >> E(es=None) + P(bf=None), catalyze_ESS_to_E_P_kc)

The catalyze_ESS_to_E_P rule's reactant side appears to be causing the issue - the enzyme's es bond should be 50, not 1.