Don't go idle if there are outstanding gets() (#2414)

Author: schmidt-sebastian

firebase-database/CHANGELOG.md

@@ -1,6 +1,8 @@
 # 19.7.0
 - [added] Added `Query.startAfter()` and `Query.endBefore()` filter for paginating
   RTDB queries.
+- [fixed] Fixed an issue with `Query.get()` that caused the client to go offline if
+  only `get()` operations were pending.
 
 # 19.6.0
 - [fixed] Fixed a crash on some Pixel devices that occurred when closing the

firebase-database/src/main/java/com/google/firebase/database/connection/PersistentConnectionImpl.java

@@ -1075,6 +1075,7 @@ private void restoreState() {
     onDisconnectRequestQueue.clear();
 
     if (logger.logsDebug()) logger.debug("Restoring reads.");
+    // Restore gets
     ArrayList<Long> outstandingGetKeys = new ArrayList<Long>(outstandingGets.keySet());
     Collections.sort(outstandingGetKeys);
     for (Long getId : outstandingGetKeys) {
@@ -1353,6 +1354,7 @@ public void run() {
    */
   private boolean isIdle() {
     return this.listens.isEmpty()
+        && this.outstandingGets.isEmpty()
         && this.requestCBHash.isEmpty()
         && !this.hasOnDisconnects
         && this.outstandingPuts.isEmpty();