Avoid checking whether the basis blades are blades (#275)

Cherry-picked from @meuns' branch.

Co-authored-by: meuns <sylvain.meunier@gmail.com>

galgebra/mv.py

@@ -984,12 +984,10 @@ def blade_coefs(self, blade_lst=None):
 
         if blade_lst is None:
             blade_lst = self.Ga.mv_blades.flat
-
-        # print 'Enter blade_coefs blade_lst =', blade_lst, type(blade_lst), [i.is_blade() for i in blade_lst]
-
-        for blade in blade_lst:
-            if not blade.is_base() or not blade.is_blade():
-                raise ValueError("%s expression isn't a basis blade" % blade)
+        else:
+            for blade in blade_lst:
+                if not blade.is_base() or not blade.is_blade():
+                    raise ValueError("%s expression isn't a basis blade" % blade)
         blade_lst = [x.obj for x in blade_lst]
         coefs, bases = metric.linear_expand(self.obj)
         coef_lst = []