Section 11. The lien shall be dissolved unless a civil action to enforce it is commenced within ninety days after the filing of the statement required by section eight. The validity of the lien shall not be affected by an inaccuracy in the description of the property to which it attaches, if the description is sufficient to identify the property, or by an inaccuracy in stating the amount due for labor or material or professional services unless it is shown that the person filing the statement has wilfully and knowingly claimed more than is due him.