Margin Accountbug simple suggested fix #868

endpoint += (isIsolated)?'/isolated':'' + '/account';

endpoint += ((isIsolated)?'/isolated':'') + '/account';

/**
 * Margin account details
 * @param {function} callback - the callback function
 * @param {boolean} isIsolated - the callback function
 * @return {undefined}
 */
mgAccount: function( callback ,isIsolated = false) {
    let endpoint = 'v1/margin';
    endpoint += ((isIsolated)?'/isolated':'') + '/account';
    signedRequest( sapi + endpoint, {}, function( error, data ) {
        if( callback ) return callback( error, data );
    } );
},