electricpy.visu.InductionMotorCircle.compute_efficiency() can divide by zero (slip and/or efficiency)

[marcostfermin]

Describe the bug

compute_efficiency() computes:

slip = rotor_cu_loss / rotor_output

and efficiency = rotor_output * 100 / (self.power_y * self.power_scale)

If rotor_output == 0 (or self.power_y == 0), it will raise ZeroDivisionError or generate inf/NaN.

This computation is visible in the module code.

https://electricpy.readthedocs.io/en/latest/_modules/electricpy/visu.html

Reproduction Code

 # Setup
import electricpy as ep

# Code which causes failure
# This is a minimal-style repro: create a circle object and force values that
# drive rotor_output to 0 (or power_y to 0). Depending on constructor behavior,
# you may need to use the class' normal initialization and then override fields.

# NOTE: If the class requires real test data to construct, you can reproduce after
# constructing normally by forcing:
#   imc.power_y = 0
# or forcing rotor_output to compute to 0 by selecting values that cancel losses.

imc = ep.visu.InductionMotorCircle(
    no_load_data=[(0, 0), (1, 0)],   # placeholder-like but valid shape
    blocked_rotor_data=[(0, 0), (1, 0)]
)

# Force a state that will trigger division by zero in compute_efficiency
imc.power_y = 0
imc.power_scale = 1
imc.power_x = 1
imc.no_load_line = [(0, 0), (1, 0)]
imc.torque_line = [(0, 0), (1, 0)]
imc.secondary_current_line = [(0, 0), (1, 0)]
imc.sync_speed = 1800

imc.compute_efficiency()

Expected behavior

Either:

handle the zero cases gracefully (return None, NaN, or a clear message), or

raise a clear, intentional exception explaining invalid operating point/data.

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: [e.g. Linux]
• Python Version [e.g. 3.7]
• Version [e.g. 0.2.1]

Additional context

The divisions are performed without guarding against rotor_output == 0 or power_y == 0.