detect when FuncDesigner does not return a solution

Sketch.py

@@ -43,7 +43,7 @@ class Sketch(object):
             print 'TODO: pad equation list'
         s = sle(equs)
         r = s.solve()
-        print 'IGNORED THINGY: ', r.ff
+        if r.ff != float('inf'):
             print "SOLVED: ", r(variables)
             for i in range(len(variables)):
                 varid_to_shape_var[i][0].setVar(varid_to_shape_var[i][1],