fixing build on Ubuntu with older Qt

src/import/objectMaker.cpp

@@ -74,7 +74,7 @@ QMap<QString, QPair<int,int> >  ObjectSignature::icmp_names;
 
 void ObjectMakerErrorTracker::registerError(const QString &msg)
 {
-    errors.append(msg);
+    if ( ! errors.contains(msg)) errors.append(msg);
     error_status = true;
 }
 

src/import/objectMaker.h

@@ -82,7 +82,7 @@ public:
     
     void registerError(const QString &msg);
     bool hasErrors() { return error_status; }
-    QStringList getErrors() { errors.removeDuplicates(); return errors; }
+    QStringList getErrors() { return errors; }
 };