优化了平衡，尤其对于向后倾倒的几种极限情况进行优化

Shibo-main-TOMMY/lib/ArduinoJson/extras/tests/JsonDocument/issue1120.cpp

@@ -0,0 +1,58 @@
+#include <ArduinoJson.h>
+
+#include <catch.hpp>
+
+TEST_CASE("Issue #1120") {
+  StaticJsonDocument<500> doc;
+  constexpr char str[] =
+      "{\"contents\":[{\"module\":\"Packet\"},{\"module\":\"Analog\"}]}";
+  deserializeJson(doc, str);
+
+  SECTION("MemberProxy<std::string>::isNull()") {
+    SECTION("returns false") {
+      auto value = doc[std::string("contents")];
+      CHECK(value.isNull() == false);
+    }
+
+    SECTION("returns true") {
+      auto value = doc[std::string("zontents")];
+      CHECK(value.isNull() == true);
+    }
+  }
+
+  SECTION("ElementProxy<MemberProxy<const char*> >::isNull()") {
+    SECTION("returns false") {  // Issue #1120
+      auto value = doc["contents"][1];
+      CHECK(value.isNull() == false);
+    }
+
+    SECTION("returns true") {
+      auto value = doc["contents"][2];
+      CHECK(value.isNull() == true);
+    }
+  }
+
+  SECTION("MemberProxy<ElementProxy<MemberProxy>, const char*>::isNull()") {
+    SECTION("returns false") {
+      auto value = doc["contents"][1]["module"];
+      CHECK(value.isNull() == false);
+    }
+
+    SECTION("returns true") {
+      auto value = doc["contents"][1]["zodule"];
+      CHECK(value.isNull() == true);
+    }
+  }
+
+  SECTION("MemberProxy<ElementProxy<MemberProxy>, std::string>::isNull()") {
+    SECTION("returns false") {
+      auto value = doc["contents"][1][std::string("module")];
+      CHECK(value.isNull() == false);
+    }
+
+    SECTION("returns true") {
+      auto value = doc["contents"][1][std::string("zodule")];
+      CHECK(value.isNull() == true);
+    }
+  }
+}