Doors: small key search optimizations

apps/openmw/mwclass/door.cpp

@@ -132,6 +132,8 @@ namespace MWClass
 
         // make key id lowercase
         std::string keyId = ptr.getCellRef().getKey();
+        if (!keyId.empty())
+        {
             Misc::StringUtils::lowerCaseInPlace(keyId);
             for (MWWorld::ConstContainerStoreIterator it = invStore.cbegin(); it != invStore.cend(); ++it)
             {
@@ -141,6 +143,8 @@ namespace MWClass
                 {
                     hasKey = true;
                     keyName = it->getClass().getName(*it);
+                    break;
+                }
             }
         }