Fix old savegames causing the save list to not fill properly (Error in framelistener: Object '$dynamic0' not found)

Fixes #1357

apps/openmw/mwgui/savegamedialog.cpp

@@ -134,9 +134,12 @@ namespace MWGui
                 else
                 {
                     // Find the localised name for this class from the store
-                    const ESM::Class* class_ = MWBase::Environment::get().getWorld()->getStore().get<ESM::Class>().find(
+                    const ESM::Class* class_ = MWBase::Environment::get().getWorld()->getStore().get<ESM::Class>().search(
                                 it->getSignature().mPlayerClassId);
-                    className = class_->mName;
+                    if (class_)
+                        className = class_->mName;
+                    else
+                        className = "?"; // From an older savegame format that did not support custom classes properly.
                 }
 
                 title << " (Level " << it->getSignature().mPlayerLevel << " " << className << ")";