Handle empty API responses

lib/www/client/source/src/store/modules/api/actions.js

@@ -4,7 +4,18 @@ async function api ({state, commit, dispatch}, [resource, init = {}]) {
 //     this.loading = true;
     const res = await fetch(`${state.apiUrl}${resource}`, init);
     if (res.ok) {
-      return await res.json();
+      try {
+        return await res.json();
+      } catch (err) {
+        if (err instanceof SyntaxError) {
+          if (Number(res.headers.get("Content-Length")) === 0) {
+            // res.json() cannot parse an empty response and we
+            // have run into this case. We just return undefined.
+            return;
+          }
+        }
+        throw err;
+      }
     } else {
       await dispatch('showSnack', [res.statusText, "warning"]);
     }