#vulnerable code 
                                public boolean isAnyExpressionQuadratic() {

        boolean retVal = false;

        String tmpExpressionKey;
        for (final Iterator<String> tmpIterator = myExpressions.keySet().iterator(); !retVal && tmpIterator.hasNext();) {
            tmpExpressionKey = tmpIterator.next();
            final Expression tmpExpression = myExpressions.get(tmpExpressionKey);
            retVal |= tmpExpression.isAnyQuadraticFactorNonZero() && (tmpExpression.isConstraint() || tmpExpression.isObjective());
        }

        return retVal;
    } 
                            #location 9 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                public boolean isAnyExpressionQuadratic() {

        boolean retVal = false;

        for (Expression value : myExpressions.values()) {
            retVal |= value.isAnyQuadraticFactorNonZero() && (value.isConstraint() || value.isObjective());
        }

        return retVal;
    }