Add warning message after load-utxo-set if bitcoin core wallet exists

contrib/FastSync/load-utxo-set.sh

@@ -97,4 +97,12 @@ BTCPAY_DATA_DIR="/var/lib/docker/volumes/generated_btcpay_datadir/_data"
 [ ! -d "$BTCPAY_DATA_DIR" ] && mkdir -p "$BTCPAY_DATA_DIR"
 echo "$TAR_NAME" > "$BTCPAY_DATA_DIR/FastSynced"
 
-echo "Successfully downloaded and extracted, you can run btcpay again (btcpay-up.sh)"
+echo "Successfully downloaded and extracted."
+
+if ! docker volume inspect generated_bitcoin_wallet_datadir &>/dev/null; then
+  echo -e '\033[33mWARNING: You need to delete your Bitcoin Core wallet before restarting with "btcpay-up.sh", or bitcoin core will fail to start.\033[0m'
+  echo -e '\033[33mDo not delete the wallet if you have any funds on it. (For example, this may be the case if you use Eclair or FullyNoded to receive funds)\033[0m'
+  echo -e '\033[33mHow to proceed: If you agree to delete your Bitcoin Core wallet, run "docker volume rm generated_bitcoin_wallet_datadir"\033[0m'
+else
+  echo "You can now run btcpay again (btcpay-up.sh)"
+fi