Cross site scripting error when browserified

[hawkmauk]

When the browserified version is compiled (for use in the playground) I get the following error when clicking the Convert from TXREF button:

Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://api.blockcypher.com/v1/btc/test3/blocks/1201739?txstart=2&limit=1. (Reason: CORS request did not succeed).

I can get around this by adding 'user-agent' to the unsafeHeaders array:

var unsafeHeaders = [    'user-agent'

Having a look through the source I don't see this variable being defined so believe it is in one of the imported modules:

grep ./external/ -R -e 'var unsafeHeaders'                                                                                                         
./external/btcr-did-tools-js/btcrDidUtils.js:var unsafeHeaders = [                                                                                                                                            
./external/btcr-did-tools-js/node_modules/es6-promise/dist/test/browserify.js:    var unsafeHeaders = {                                                                                                       
./external/btcr-did-tools-js/node_modules/stream-http/lib/request.js:var unsafeHeaders = [                                                                                                                    
./external/btcr-did-tools-js/node_modules/txref-conversion-js/txrefConverter-browserified.js:var unsafeHeaders = [                                                                                            
./external/txref-conversion-js/txrefConverter-browserified.js:var unsafeHeaders = [