Bug Fix: Cleanup of string stack bad Eval

In Torsion i've found cases where an EVAL of an expression like this...

ObjectThatDoesNotExist.getId();

Will return seemingly random results in the watch window. This is because Torque is not clearing the string stack in this particular case and whatever was left from a previous evaluation is returned. To fix this we must change the following in compiledEval.cc/.cpp:

case OP_CALLFUNC:
         {
            // ...

            else if(callType == FuncCallExprNode::MethodCall)
            {
               saveObject = gEvalState.thisObject;
               gEvalState.thisObject = Sim::findObject(callArgv[1]);
               if(!gEvalState.thisObject)
               {
                  gEvalState.thisObject = 0;
                  Con::warnf(ConsoleLogEntry::General,"%s: Unable to find object: '%s' attempting to call function '%s'", getFileLine(ip-4), callArgv[1], fnName);
                  STR.setStringValue(""); // ADDED... cleanup the string stack!
                  break;
               }

My testing so far shows that this is a good fix. Furthermore looking thru the code in OP_CALLFUNC you'll find several other cases where the string value is cleared like in this section...

if(nsEntry->mType == Namespace::Entry::ScriptFunctionType)
            {
               if(nsEntry->mFunctionOffset)
                  nsEntry->mCode->exec(nsEntry->mFunctionOffset, fnName, nsEntry->mNamespace, callArgc, callArgv, false, nsEntry->mPackage);
               else // no body
                  STR.setStringValue("");
            }

So i think this is a good fix and should be added to HEAD.