Improve fix wrong code generation if EN/ENO are used in FBD/LD/SFC

Commit c9915bc6 "Fix wrong code generation if EN/ENO are used in
FBD/LD/SFC" caused following backtrace in some cases:

File "/home/developer/WorkData/PLC/beremiz/beremiz/PLCGenerator.py", line 476, in GenerateProgram
self.GeneratePouProgram(pou_name)
File "/home/developer/WorkData/PLC/beremiz/beremiz/PLCGenerator.py", line 258, in GeneratePouProgram
program = pou_program.GenerateProgram(pou)
File "/home/developer/WorkData/PLC/beremiz/beremiz/PLCGenerator.py", line 1713, in GenerateProgram
self.ComputeProgram(pou)
File "/home/developer/WorkData/PLC/beremiz/beremiz/PLCGenerator.py", line 997, in ComputeProgram
eno_var = self.GetUsedEno(body, connections)
File "/home/developer/WorkData/PLC/beremiz/beremiz/PLCGenerator.py", line 929, in GetUsedEno
for invar in blk.inputVariables.getvariable():
File "/home/developer/WorkData/PLC/beremiz/beremiz/xmlclass/xmlclass.py", line 1363, in getattrMethod
return DefaultElementClass.__getattribute__(self, name)
<type 'exceptions.AttributeError'>: 'inOutVariable' object has no attribute 'inputVariables'

// import Nevow.Athena

function init() {
  Nevow.Athena.Widget.fromAthenaID(1).callRemote('HMIexec', 'HMIinitialisation');
}

WebInterface.PLC = Nevow.Athena.Widget.subclass('WebInterface.PLC');
WebInterface.PLC.method(
	 'updateHMI',
	 function (self, data) {
	   d = self.callRemote('getPLCElement');
	   d.addCallback(
			 function liveElementReceived(le) {
				d2 = self.addChildWidgetFromWidgetInfo(le);
				d2.addCallback(
						function childAdded(widget) {
						var node = self.nodeById('content');
						node.replaceChild(widget.node, node.getElementsByTagName('div')[0]);
						init();
						});
				});
	   });

Divmod.Base.addLoadEvent(init);