log if memory allocation for live view fails

Explained in #591

src/WebApi_ws_live.cpp

@@ -68,6 +68,14 @@ void WebApiWsLiveClass::loop()
         try {
             std::lock_guard<std::mutex> lock(_mutex);
             DynamicJsonDocument root(4200 * INV_MAX_COUNT); // TODO(helge) check if this calculation is correct
+
+            // TODO(helge) temporary dump of memory usage if allocation of DynamicJsonDocument fails (will be fixed in upstream repo)
+            if (root.capacity() == 0) {
+                MessageOutput.printf("Calling /api/livedata/status has temporarily run out of resources. Reason: Alloc memory for DynamicJsonDocument failed (FreeHeap = %d, MaxAllocHeap = %d, MinFreeHeap = %d).\r\n", ESP.getFreeHeap(), ESP.getMaxAllocHeap(), ESP.getMinFreeHeap());
+                _lastWsPublish = millis();
+                return;
+            }
+
             JsonVariant var = root;
             generateJsonResponse(var);