Description of the problem

I'm trying to plot two vectors using the following script. It works well if pen is set to 1p,black (i.e. a simple line), but crashes if set to 1p,black+ve0.2c. Actually, the first plot works, but the second one crashes.

Full code that generated the error

import pygmt
import numpy as np

fig = pygmt.Figure()
fig.basemap(projection="X15c/10c", region="400/600/5/8", frame=True)
fig.plot(x=[530.0, 530.0], y=[6.0, 7.0], pen='1p,black+ve0.2c')
fig.plot(x=[570.0, 570.0], y=[6.0, 7.0], pen='1p,black+ve0.2c')
fig.savefig("map.pdf")

Full error message

python(64354,0x11ac3bdc0) malloc: *** error for object 0x7f8f28e50900: pointer being freed was not allocated
python(64354,0x11ac3bdc0) malloc: *** set a breakpoint in malloc_error_break to debug
[1]    64354 abort      python test.py

System information

• Operating system: macOS
• Python installation (Anaconda, system, ETS): Anaconda
• Version of GMT: 6.1.0_e6eb3b9_2020.03.30
• Version of Python: 3.7.4
• Version of this package: 0.0.1a0+75.g088b0d1
• If using conda, paste the output of conda list below:

PASTE OUTPUT OF CONDA LIST HERE