fix build error (#202)

Author: imbissbudenaesthetik

app/src/main/java/de/seemoo/at_tracking_detection/database/repository/DeviceRepository.kt

@@ -3,6 +3,7 @@ package de.seemoo.at_tracking_detection.database.repository
 import androidx.annotation.WorkerThread
 import de.seemoo.at_tracking_detection.database.daos.DeviceDao
 import de.seemoo.at_tracking_detection.database.models.device.BaseDevice
+import de.seemoo.at_tracking_detection.database.models.device.ConnectionState
 import de.seemoo.at_tracking_detection.database.models.device.DeviceType
 import de.seemoo.at_tracking_detection.database.relations.DeviceBeaconNotification
 import de.seemoo.at_tracking_detection.util.Utility