Add check for solenoid in case of thin l=0 solenoid

Author: jgray-19

src/madl_etrck.mad

@@ -297,7 +297,7 @@ end
 local function track_multipole (elm, m)
   get_mult(elm, m) ; adj_mult(m)
 
-  if m.nmul == 0 then return track_marker(elm, m) end
+  if m.nmul == 0 and abs(elm.ksi) < minstr then return track_marker(elm, m) end
 
   local angle, ksi, lrad in elm
   local knl, ksl in m