Store IDs only for tasks with acquired quotas

Avoids populating the internal task tracking map with entries for task
IDs that did not acquire any quotas. Previously, `quotasByTask` was
updated for all tasks regardless of whether any quotas were actually
obtained.

This change ensures that only tasks with acquired quotas are recorded,
which reduces memory usage in high-concurrency environments where many
threads may run without being throttled.

Change-Id: I9567af641c78ab6eb6c824fef68ec68777abf552

src/main/java/com/googlesource/gerrit/plugins/quota/TaskQuotas.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/quota/TaskQuotas.java b/src/main/java/com/googlesource/gerrit/plugins/quota/TaskQuotas.java
index 4050dcc..b59d6f8 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/quota/TaskQuotas.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/quota/TaskQuotas.java
@@ -56,7 +56,9 @@
       }
     }
 
-    quotasByTask.put(task.getTaskId(), acquiredQuotas);
+    if (!acquiredQuotas.isEmpty()) {
+      quotasByTask.put(task.getTaskId(), acquiredQuotas);
+    }
     return true;
   }