[BUG] Prediction fails on circuits of one element about impedance.py HOT 2 CLOSED

from impedance.models.circuits import CustomCircuit
import numpy as np
test_circuit = CustomCircuit(circuit='R_1', initial_guess = [1.0,])
print(test_circuit)
frequency_range = np.linspace(0,100)
test_circuit.predict(frequency_range)

Circuit string: R_1
Fit: False

Initial guesses:
    R_1 = 1.00e+00 [Ohm]

Simulating circuit based on initial parameters
---------------------------------------------------------------------------
UnboundLocalError                         Traceback (most recent call last)
<ipython-input-10-cbc428542153> in <module>
      4 print(test_circuit)
      5 frequency_range = np.linspace(0,100)
----> 6 test_circuit.predict(frequency_range)

~/Documents/Programs/impedance.py/impedance/models/circuits/circuits.py in predict(self, frequencies, use_initial)
    156                                      *self.initial_guess,
    157                                      constants=self.constants, eval_string='',
--> 158                                      index=0)[0],
    159                         circuit_elements)
    160 

~/Documents/Programs/impedance.py/impedance/models/circuits/fitting.py in buildCircuit(circuit, frequencies, constants, eval_string, index, *parameters)
    204         split = parallel
    205 
--> 206     for i, elem in enumerate(split):
    207         if ',' in elem or '-' in elem:
    208             eval_string, index = buildCircuit(elem, frequencies,

UnboundLocalError: local variable 'split' referenced before assignment

parallel = parse_circuit(circuit, parallel=True)
series = parse_circuit(circuit, series=True)

if series is not None and len(series) > 1:
    eval_string += "s(["
    split = series
elif parallel is not None and len(parallel) > 1:
    eval_string += "p(["
    split = parallel

for i, elem in enumerate(split):