only do IP geolocation on step 3 of subscription-based AAQs

https://github.com/mozilla/sumo-project/issues/957

kitsune/sumo/static/sumo/js/location.es6

@@ -1,14 +1,18 @@
 window.addEventListener("DOMContentLoaded", (event) => {
     const geoIPUrl = 'https://location.services.mozilla.com/v1/country?key=fa6d7fc9-e091-4be1-b6c1-5ada5815ae9d';
-    fetch(geoIPUrl)
-    .then(response => {
-        if (!response.ok) {
-            throw new Error(`Fetch failed, status ${response.status}`)
-        }
-        return response.json();
+    const countryField = document.querySelector('input#id_country');
 
-    })
-    .then(data => {
-        document.getElementById("id_country").value = data.country_name;
-    })
+    if (countryField) {
+        fetch(geoIPUrl)
+        .then(response => {
+            if (!response.ok) {
+                throw new Error(`Fetch failed, status ${response.status}`)
+            }
+            return response.json();
+
+        })
+        .then(data => {
+            countryField.value = data.country_name;
+        })
+    }
 });