Return NULL if the node extensions doesn't have 5 elements

The check is needed because simply returning 5th element could result
in garbage being returned as pinning array pointer. Returning non null
pinning array pointer when it wasn't set can lead to runtime failures.

Signed-off-by: Shubham Verma <shubhamv.sv@gmail.com>

compiler/il/OMRNode.cpp

@@ -5214,7 +5214,7 @@ OMR::Node::getPinningArrayPointer()
    if (self()->getOpCode().hasPinningArrayPointer())
       return _unionPropertyA._pinningArrayPointer;
 
-   return _unionBase._extension.getExtensionPtr()->getElem<TR::AutomaticSymbol *>(5);
+   return _unionBase._extension.getNumElems() >= 6 ? _unionBase._extension.getExtensionPtr()->getElem<TR::AutomaticSymbol *>(5) : NULL;
    }
 
 TR::AutomaticSymbol*