fix: missing null check

lib/encryption/utils/key_verification.dart

@@ -603,6 +603,9 @@ class KeyVerification {
               '[Key Verification] Tried to broadcast and un-broadcastable type: $type');
         }
       } else {
+        if (client.userDeviceKeys[userId].deviceKeys[deviceId] == null) {
+          Logs().e('[Key Verification] Unknown device');
+        }
         await client.sendToDeviceEncrypted(
             [client.userDeviceKeys[userId].deviceKeys[deviceId]],
             type,

lib/src/client.dart

@@ -1963,6 +1963,7 @@ class Client extends MatrixApi {
     // then only send it to verified devices
     if (deviceKeys.isNotEmpty) {
       deviceKeys.removeWhere((DeviceKeys deviceKeys) =>
+          deviceKeys == null ||
           deviceKeys.blocked ||
           (deviceKeys.userId == userID && deviceKeys.deviceId == deviceID) ||
           (onlyVerified && !deviceKeys.verified));