QAOA missing _expectation

[nonhermitian]

Information

• Qiskit Aqua version: master
• Python version:
• Operating system:

What is the current behavior?

/opt/miniconda3/lib/python3.7/site-packages/qiskit_aqua-0.7.0-py3.7.egg/qiskit/aqua/algorithms/minimum_eigen_solvers/vqe.py in quantum_instance(self, quantum_instance)
    184             self._circuit_sampler.quantum_instance = self._quantum_instance
    185 
--> 186         if self._expectation is None:
    187             self._try_set_expectation_value_from_factory()
    188 

AttributeError: 'QAOA' object has no attribute '_expectation'

Steps to reproduce the problem

What is the expected behavior?

Suggested solutions