[FIX] btc2ripple right error message (RT-3412)

fix error message on add btc2ripple confirm
dialog if email is already in use

src/templates/tabs/btc.jade

@@ -61,7 +61,7 @@ section.col-xs-12.content(ng-controller='BtcCtrl')
               .col-xs-7.col-sm-5.col-md-4
                 rp-popup
                   a.btn.btn-success.btn-sm.btn-block.sign(href="", rp-popup-link,
-                    ng-click="openPopup()", ng-show="!btcConnected && !loading && !loadingAccount && loadState.B2RApp", ng-disabled="emailError", ng-hide="btcConnected",l10n) Add btc2ripple
+                    ng-click="openPopup()", ng-show="!btcConnected && !loading && !loadingAccount && loadState.B2RApp", ng-disabled="emailError || !account.Balance || !can_add_trust", ng-hide="btcConnected",l10n) Add btc2ripple
                   div.connectModal(rp-popup-content)
                     .modal-header
                       .navbar-brand.hidden-sm.modal-logo#logo
@@ -82,9 +82,12 @@ section.col-xs-12.content(ng-controller='BtcCtrl')
                           span(ng-hide="loading", l10n) Confirm
                         button.modal-btn.btn.btn-default.btn-link.btn-cancel(data-dismiss="modal"
                           ng-hide="loading", l10n) cancel
-                      span.modal-error(ng-show="emailError", l10n)
+                      span.modal-error(ng-show="generalError", l10n)
                         | SnapSwap's btc2ripple service is currently unavailable.
                         |  Please check back later.
+                      div.modal-error(ng-show="emailError", l10n)
+                        | You’ve already used this email address to generate a bitcoin receiving address in Ripple Trade.
+                        | Please contact [email protected] if you want to use this Ripple Trade account instead.
                 button.btn.btn-primary(ng-show="!btcConnected && loading", ng-disabled="loading", l10n) Adding...
                 button.btn.btn-block.btn-primary(ng-show="showInstructions && btcConnected", type="submit", ng-click="toggle_instructions()", l10n) Hide instructions
                 button.btn.btn-block.btn-primary(ng-show="btcConnected && !showInstructions", type="submit", ng-click="toggle_instructions()", l10n) Show instructions