unexpected minor ticks in colorbar

[Kinya Toride]

Description

I found a minor bug that when we plot a colorbar twice, unexpected minor ticks appear in the first colorbar.

Steps to reproduce

import numpy as np
import proplot as pplt

state = np.random.RandomState(51423)
data = 1 + (state.rand(12, 10) - 0.45).cumsum(axis=0)

fig, ax = pplt.subplots()

m = ax.pcolor(data)
ax.colorbar(m)
ax.colorbar(m)

Equivalent steps in matplotlib

import numpy as np
import matplotlib.pyplot as plt
state = np.random.RandomState(51423)
data = 1 + (state.rand(12, 10) - 0.45).cumsum(axis=0)

fig, ax = plt.subplots()

m = ax.pcolor(data)
plt.colorbar(m)
plt.colorbar(m)

Proplot version

3.4.3
0.9.5