Fixed crash in Set Constrain->Percentage in Edge mode,

Was happening after have picked the axis for Set
Constrain->Percentage in Edge mode.

The problem was reported in this post: http://www.wings3d.com/forum/showthread.php?tid=718

NOTE: Fixed crash in Set Constrain->Percentage in Edge mode,
      Thanks Arg Arg.

plugins_src/commands/wpc_constraints.erl

@@ -344,29 +344,29 @@ command({_Mode,{set_constraint,{to_axis,{none,Axis2}}}},St) ->
 %%% Scale Edge Mode
 command({edge,{set_constraint,{scale,{'ASK','ASK'}}}},St) ->
     wings:ask(selection_ask([along_axis1,along_axis2]), St,
-      fun({Pn0,Pp0,Pn1,Pp1},St0) ->
-          scale({{Pn0,Pp0},{Pn1,Pp1}},St0)
+      fun({Pn0,Pn1},St0) ->
+          scale({Pn0,Pn1},St0)
     end);
 command({edge,{set_constraint,{scale,{'ASK',none}}}},St) ->
-    wings:ask(selection_ask([along_axis1]), St, fun({Pn1,Pp1},St0) ->
-        scale({{Pn1,Pp1},{Pn1,Pp1}},St0)
+    wings:ask(selection_ask([along_axis1]), St, fun(Pn1,St0) ->
+        scale({Pn1,Pn1},St0)
     end);
 command({edge,{set_constraint,{scale,{'ASK',Axis2}}}},St) ->
-    wings:ask(selection_ask([along_axis1]), St, fun({Pn1,Pp1},St0) ->
-        scale({{Pn1,Pp1},Axis2},St0)
+    wings:ask(selection_ask([along_axis1]), St, fun({Pn1},St0) ->
+        scale({Pn1,Axis2},St0)
     end);
 command({edge,{set_constraint,{scale,{Axis1,'ASK'}}}},St) ->
-    wings:ask(selection_ask([along_axis2]), St, fun({Pn1,Pp1},St0) ->
-        scale({Axis1,{Pn1,Pp1}},St0)
+    wings:ask(selection_ask([along_axis2]), St, fun({Pn1},St0) ->
+        scale({Axis1,Pn1},St0)
     end);
 command({edge,{set_constraint,{scale,{Axis1,none}}}},St) ->
     scale({Axis1,Axis1},St);
 command({edge,{set_constraint,{scale,{Axis1,Axis2}}}},St) ->
     scale({Axis1,Axis2},St);
 command({edge,{set_constraint,{scale,_}}},St) ->
     wings:ask(selection_ask([along_axis1,along_axis2]), St,
-      fun({Pn0,Pp0,Pn1,Pp1},St0) ->
-          scale({{Pn0,Pp0},{Pn1,Pp1}},St0)
+      fun({Pn0,Pn1},St0) ->
+          scale({Pn0,Pn1},St0)
     end);
 
 %%% Scale Face Mode