Information

Qiskit Terra version: 0.15.1
Python version: 3.7.7
Operating system: MacOS v10.15.6

What is the current behavior?

When two QuantumCircuit objects are compared with == and one of them is None, an error is thrown.

Steps to reproduce the problem

from qiskit import QuantumCircuit
qc1 = QuantumCircuit()
qc2 = None
qc1 == qc2 --> error

What is the expected behavior?

The qc1 == qc2 comparison should always return True or False.