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

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# This file is part of Beremiz.
# See COPYING file for copyrights details.

from __future__ import absolute_import
import os
from lxml import etree
import util.paths as paths
from plcopen.structures import StdBlckLibs

ScriptDirectory = paths.AbsDir(__file__)


class XSLTModelQuery(object):
    """ a class to handle XSLT queries on project and libs """
    def __init__(self, controller, xsltpath, ext=None):
        # arbitrary set debug to false, updated later
        self.debug = False

        # merge xslt extensions for library access to query specific ones
        xsltext = [
            ("GetProject", lambda *_ignored:
             [controller.GetProject(self.debug)]),
            ("GetStdLibs", lambda *_ignored:
             [lib for lib in StdBlckLibs.values()]),
            ("GetExtensions", lambda *_ignored:
             [ctn["types"] for ctn in controller.ConfNodeTypes])
        ]

        if ext is not None:
            xsltext.extend(ext)

        # parse and compile. "beremiz" arbitrary namespace for extensions
        self.xslt = etree.XSLT(
            etree.parse(
                os.path.join(ScriptDirectory, xsltpath),
                etree.XMLParser()),
            extensions={("beremiz", name): call for name, call in xsltext})

    def _process_xslt(self, root, debug, **kwargs):
        self.debug = debug
        res = self.xslt(root, **{k: etree.XSLT.strparam(v) for k, v in kwargs.iteritems()})
        # print(self.xslt.error_log)
        return res


# -------------------------------------------------------------------------------
#           Helpers functions for translating list of arguments
#                       from xslt to valid arguments
# -------------------------------------------------------------------------------


def _StringValue(x):
    return x


def _BoolValue(x):
    return x in ["true", "0"]


def _translate_args(translations, args):
    return [translate(arg[0]) if len(arg) > 0 else None
            for translate, arg in
            zip(translations, args)]