Fix favicon corruption on loading database

* Fix #2251 and Fix #2674
* Icons stored with duplicate UUID's will be
assigned a new UUID on load. This causes entries
using the duplicate UUID to display the default icon.

src/format/KdbxXmlReader.cpp

@@ -367,6 +367,10 @@ void KdbxXmlReader::parseIcon()
     }
 
     if (uuidSet && iconSet) {
+        // Check for duplicate UUID (corruption)
+        if (m_meta->containsCustomIcon(uuid)) {
+            uuid = QUuid::createUuid();
+        }
         m_meta->addCustomIcon(uuid, icon);
         return;
     }