message: fix page title referencing nonexistent model prop
diff: -{{page-title (concat "Pay Merchant: " (or @model.merchant.name @model.merchantSafeID)) replace=true}}
  +{{page-title (concat "Pay Merchant: " (or @model.merchant.name @model.merchantSafe.address)) replace=true}}
  <div class="merchant-payment-request-page">
  