Donation Receipts 2.2.11

Changes since 2.2.10

• [#159] Avoid Call to a member function getProfile() on null errors during contribution validation - by @jensschuppe
• [#170] Do not overwrite the issued_on field when copying a donation receipt - by @MarcMichalsky
• [#174] Fix array_multisort error - by @jensschuppe

Full Changelog: 2.2.10...2.2.11