Fix edges with hinge eye(s)

Thanks to https://github.com/werner4711 for reporting and
https://github.com/gpsqueeek for pointing out that d4b238c was the
culprit.

Resolves: #742

boxes/edges.py

@@ -1456,7 +1456,7 @@ def endwidth(self) -> float:
 
     def margin(self) -> float:
         if self.settings.outset and (
-                self.grip_percentage > 0.0 or
+                self.settings.grip_percentage > 0.0 or
                 self.settings.grip_length > 0.0 ):
             return self.settings.thickness + self.boxes.edges['g'].margin()
         else: