fix: ignore https mappings when no ssl certificate exists

This fixes issues where users may somehow add an https mapping but are missing an ssl certificate, causing nginx to not load properly. We now ignore the mapping and warn users of the misconfiguration.

Closes #5368

tests/unit/test_helper.bash

@@ -366,6 +366,11 @@ setup_test_tls() {
   sudo chown -R dokku:dokku "${TLS}/.."
 }
 
+teardown_test_tls() {
+  local TLS="/home/dokku/$TEST_APP/tls"
+  rm -rf "$TLS"
+}
+
 custom_ssl_nginx_template() {
   local APP="$1"
   local APP_REPO_DIR="$2"