corrected usage of "append" (which does not copy list items but only creates references)

processing/pre/mentat_pbcOnBoxMesh.py

@@ -116,7 +116,8 @@ def servoLink():
     for dir in xrange(3):                         # check for each direction
       if node['faceMember'][dir]:                 # me on this front face
         linkCoord[0][dir] = box['min'][dir]       # project me onto rear face along dir
-        linkCoord.append(box['min'])            # append base corner
+        linkCoord.append(numpy.array(box['min'])) # append base corner
+        
         linkCoord[-1][dir] = box['max'][dir]      # stretch it to corresponding control leg of "dir"
 
     nLinks = len(linkCoord)