GET unless POSTing data

ext/bg/js/ankiweb.js

@@ -155,9 +155,14 @@ class AnkiWeb {
             const xhr = new XMLHttpRequest();
             xhr.addEventListener('error', () => reject('failed to execute network request'));
             xhr.addEventListener('load', () => resolve(xhr.responseText));
+            if (dataEnc) {
                 xhr.open('POST', url);
                 xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
                 xhr.send(dataEnc);
+            } else {
+                xhr.open('GET', url);
+                xhr.send();
+            }
         });
     }
 }