object is null in class AbstractOMNeTARAClient

[mfrey]

A bug reported by the clang static analyzer.

Description: Called C++ object pointer is null
File: AbstractOMNeTARAClient.cpp
Lines: 100, 200, and 206

omnetpp/AbstractOMNeTARAClient.cpp:100:26: warning: Called C++ object pointer is null
    int nrOfInterfaces = interfaceTable->getNumInterfaces();
                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
omnetpp/AbstractOMNeTARAClient.cpp:200:37: warning: Called C++ object pointer is null
        cPacket* encapsulatedData = simPacket->decapsulate();
                                    ^~~~~~~~~~~~~~~~~~~~~~~~
omnetpp/AbstractOMNeTARAClient.cpp:206:9: warning: Called C++ object pointer is null
        encapsulatedData->setControlInfo(controlInfo);
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
3 warnings generated.

[mfrey]

The issue in line 200 and 206 refer to a (maybe) failing dynamic_cast. Hence, added a check. The same goes for the issue in line 100. The interfaceTable might not be initialized. However, the assert should avoid that subsequent calls are made. For the sake of clarity and for the static analyzer, I've added a check on the pointer.