a fix to compute_jost_withnan_dumb that won't work

jass/models/worktable.py

@@ -111,7 +111,7 @@ def make_compute_jost_nonan(cov):
 def make_compute_jost_withnan_dumb(cov):
     def compute_jost_withnan_dumb(z):
         whichnan = np.where(np.logical_not(np.isnan(z)))
-        invcov = np.linalg.inv(cov[whichnan, whichnan])
+        invcov = np.linalg.inv(cov.iloc[whichnan, whichnan])
         znonan = z[whichnan]
         p = znonan.shape[0]
         chi = np.sum(np.multiply(znonan, znonan.dot(invcov)))