plt.errorbar error with empty list

[divenex]

The command below returns an error in Matplotlib 1.5.0

plt.errorbar([], [], xerr=[], yerr=[])

Even tough

plt.errorbar([], [])

works as expected.

When the x and y coordinates are empty lists, It would make sense for the command to accept empty xerr and yerr keywords as well, without throwing an error, as in the previous Matplotlib version. In fact the empty lists will likely come from code like the following, where np.any(mask)==False

mask = y > 0
plt.errorbar(x[mask], y[mask], xerr=xerr[mask], yerr=yerr[mask])

[mdboom]

Related to #5572, suggesting we need a general solution to this problem as hinted at in the comments over there.

[tacaswell]

Were we just not laundering enough inputs through the unit frame work before?