Broken gateway links on deposit and withdraw page

**Describe the bug**

Broken "Pirate" and "Xbts Native Chains" gateway links on the deposit page and the withdraw page.

**To Reproduce**
Steps to reproduce the behavior:
1. Go to https://develop.bitshares.org
2. Navigate to an account, or login
3. Select default gateway services (as of writing, options are: BlockTrades, ioxbank, Pirate, and Xbts Native Chains)
4. Click on Hamburg Menu - Deposit
5. Select 'BTC'
6. Select a gateway (as of writing, options are: "Pirate" and "Xbts Native Chains")
7. click the "?" icon right to "GATEWAY"
8. See result: the help menu tree shows in the background with no other content
9. Similar issue on the withdraw page

**Expected behavior**
The correct page appears if it exists; if it does not exist, show an error message indicating that the page does not exist, or maybe do not show the "?" icon at all.

**Screenshots**

**Desktop (please complete the following information):**
- OS: Ubuntu 18.04
- Browser: Chrome
- Version: Latest

**Additional context**
* The link to the `ioxbank` gateway help page is correct (select XRP or XLM to see).
* There is a help page for the "xbts" gateway, but neither the link on the deposit nor on the withdraw page is correct.
* The is no help page for the "Pirate" gateway

Start by reproducing the broken links on the deposit and withdraw pages at https://develop.bitshares.org, following the reported BTC gateway flow for Pirate and Xbts Native Chains. Inspect how the gateway help link is selected and compare it with the working ioxbank link and the existing xbts help page. Done means valid help content appears, or the link/icon is omitted or shows an explicit missing-page error.

Written by the indexing model from the issue text.