Rewrite limitConcurrency to fix error catching

Make sure that we only catch errors that are a result of
calling fn()

src/stores/GroupStore.js

@@ -48,30 +48,30 @@ function checkBacklog() {
 
 // Limit the maximum number of ongoing promises returned by fn to LIMIT and
 // use a FIFO queue to handle the backlog.
-function limitConcurrency(fn) {
+async function limitConcurrency(fn) {
-    return new Promise((resolve, reject) => {
+    if (ongoingRequestCount >= LIMIT) {
-        const item = () => {
+        // Enqueue this request for later execution
-            ongoingRequestCount++;
+        await new Promise((resolve, reject) => {
-            resolve();
+            backlogQueue.push(resolve);
-        };
+        });
-        if (ongoingRequestCount >= LIMIT) {
+    }
-            // Enqueue this request for later execution
+
-            backlogQueue.push(item);
+    let result;
-        } else {
+    let error;
-            item();
+
-        }
+    ongoingRequestCount++;
-    })
+    try {
-    .then(fn)
+        result = await fn();
-    .catch((err) => {
+    } catch (err) {
+        error = err;
+    } finally {
         ongoingRequestCount--;
         checkBacklog();
-        throw err;
+    }
-    })
+
-    .then((result) => {
+    if (error) throw error;
-        ongoingRequestCount--;
+
-        checkBacklog();
+    return result;
-        return result;
-    });
 }
 
 /**