added a smidge of code to assemble.stats to dropna(axis=1, how='all') to

drop all columns (axis=1) where all results are NaN

ipyrad/core/assembly.py

@@ -138,7 +138,7 @@ def stats(self):
         nameordered = self.samples.keys()
         nameordered.sort()
         return pd.DataFrame([self.samples[i].stats for i in nameordered], 
-                      index=nameordered)
+                      index=nameordered).dropna( axis=1, how='all')
                       #dtype=[int, int, int, int, int, float, float, int])