Fix crash if LD input contact isn't connected

Traceback (most recent call last):
File "/home/developer/WorkData/PLC/beremiz/beremiz/BeremizIDE.py", line 339, in OnMethod
obj.CTR.CallMethod('_'+meth)
File "/home/developer/WorkData/PLC/beremiz/beremiz/ProjectController.py", line 1996, in CallMethod
getattr(self, method)()
File "/home/developer/WorkData/PLC/beremiz/beremiz/ProjectController.py", line 1134, in _Build
IECGenRes = self._Generate_SoftPLC()
File "/home/developer/WorkData/PLC/beremiz/beremiz/ProjectController.py", line 746, in _Generate_SoftPLC
if self._Generate_PLC_ST():
File "/home/developer/WorkData/PLC/beremiz/beremiz/ProjectController.py", line 763, in _Generate_PLC_ST
self._getIECgeneratedcodepath())
File "/home/developer/WorkData/PLC/beremiz/beremiz/PLCControler.py", line 456, in GenerateProgram
self.ProgramChunks = GenerateCurrentProgram(self, self.Project, errors, warnings)
File "/home/developer/WorkData/PLC/beremiz/beremiz/PLCGenerator.py", line 1762, in GenerateCurrentProgram
generator.GenerateProgram()
File "/home/developer/WorkData/PLC/beremiz/beremiz/PLCGenerator.py", line 478, in GenerateProgram
self.GeneratePouProgram(pou_name)
File "/home/developer/WorkData/PLC/beremiz/beremiz/PLCGenerator.py", line 260, in GeneratePouProgram
program = pou_program.GenerateProgram(pou)
File "/home/developer/WorkData/PLC/beremiz/beremiz/PLCGenerator.py", line 1718, in GenerateProgram
self.ComputeProgram(pou)
File "/home/developer/WorkData/PLC/beremiz/beremiz/PLCGenerator.py", line 1028, in ComputeProgram
self.GenerateBlock(instance, block_infos, body, None)
File "/home/developer/WorkData/PLC/beremiz/beremiz/PLCGenerator.py", line 1144, in GenerateBlock
expression = self.ComputeExpression(body, connections, executionOrderId > 0)
File "/home/developer/WorkData/PLC/beremiz/beremiz/PLCGenerator.py", line 1373, in ComputeExpression
paths = self.GeneratePaths(connections, body, order, to_inout)
File "/home/developer/WorkData/PLC/beremiz/beremiz/PLCGenerator.py", line 1344, in GeneratePaths
elif isinstance(result[0], list):
IndexError: list index out of range


Close #70

/* This project contains wamp client config to be loaded at runtime startup. */
./project_files/wampconf.json

wampconf.json is in "Project Files", so it is copied to runtime's working directory, and then loaded after program transfer + runtime restart.

Otherwise, wamp config file path can be forced :
./Beremiz_service.py -c /path/to/my/wampconf.json /working/dir

/* Crossbar install */
#sudo apt-get update
#sudo apt-get -y dist-upgrade
sudo apt-get -y install build-essential libssl-dev libffi-dev libreadline-dev libbz2-dev libsqlite3-dev libncurses5dev
sudo apt-get -y install python3-pip
sudo python3 -m pip install -U pip
sudo pip3 install crossbar
crossbar version

/* Start Crossbar command: */
crossbar start

/* Crossbar test router configuration is available in .crossbar directory. */
Tested on version:

    :::::::::::::::::
          :::::          _____                      __
    :::::   :   :::::   / ___/____ ___   ___  ___  / /  ___ _ ____
    :::::::   :::::::  / /__ / __// _ \ (_-< (_-< / _ \/ _ `// __/
    :::::   :   :::::  \___//_/   \___//___//___//_.__/\_,_//_/
          :::::
    :::::::::::::::::   Crossbar v18.7.2

    Copyright (c) 2013-2018 Crossbar.io Technologies GmbH, licensed under AGPL 3.0.

 Crossbar.io        : 18.7.2
   Autobahn         : 18.7.1
   Twisted          : 18.7.0-EPollReactor
   LMDB             : 0.94/lmdb-0.9.22
   Python           : 3.6.6/CPython
 Frozen executable  : no
 Operating system   : Linux-4.16.0-2-rt-amd64-x86_64-with-debian-buster-sid
 Host machine       : x86_64
 Release key        : RWS9T4NltFjmKSMbEtETnOMxRjLhOEZ6e80T5MYzTTh/+NP9Jk20sJmA