Fixing dupX method

Author: VincenzoArceri

src/main/java/it/unipr/analysis/taint/TaintAbstractStack.java

@@ -941,14 +941,14 @@ private TaintAbstractStack dupX(int x, TaintAbstractStack stack) {
 
 		TaintElement tmp = (TaintElement) obj[first - x];
 
-		clone.add(tmp);
-		clone.remove(0);
-
 		ArrayList<TaintElement> result = new ArrayList<>();
 
 		for (int i = 0; i < clone.size(); i++)
 			result.add((TaintElement) obj[i]);
 
+		result.add(tmp);
+		result.remove(0);
+
 		return new TaintAbstractStack(result);
 	}