These errors simply indicate that you have not provided URI templates for a blockexplorer to your coin.
Please see https://www.dashed-slug.net/bitcoin-altcoin-wallets-wordpress-plugin/full-node-multi-coin-adapter-extension/ for an example of how to add a coin.
If you are encountering white screen errors then there will be other errors in your logs besides this one. Fix this issue, then observe the logs a bit more.
If there is no blockexplorer for this coin, then simply set the two fields to empty strings, i.e.
'explorer tx uri' => '',
'explorer address uri' => '',