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'

include yslt.yml2

in xsl {
    decl istylesheet (
        *output="xml",
        version="1.0",
        xmlns:xsl="http://www.w3.org/1999/XSL/Transform",
        xmlns:exsl='http://exslt.org/common',
        extension-element-prefixes='exsl'
    ) alias stylesheet {
        output *output;
        content;
    };

    decl template(match) {
        content;
    };

    decl function(name) alias template {
        content;
    };
   
    decl call(name) alias call-template {
        content;
    };

    decl apply(select) alias apply-templates {
        content;
    };
}