Fix crash when building history changes

* Replace rarely hit asserts with defined nullptr checks when replacing references without a group
* Fix #7603
* Replace TOTP history comparison with checking the actual TOTP output instead of a compiled string

src/gui/entry/EntryHistoryModel.cpp

@@ -232,7 +232,7 @@ void EntryHistoryModel::calculateHistoryModifications()
             || curr->timeInfo().expiryTime() != compare->timeInfo().expiryTime()) {
             modifiedFields << tr("Expiration");
         }
-        if (curr->totpSettingsString() != compare->totpSettingsString()) {
+        if (curr->totp() != compare->totp()) {
             modifiedFields << tr("TOTP");
         }
         if (*curr->customData() != *compare->customData()) {