Extract getOrCreateMember()

Before: 9802, 8568, 9630, 12434, 9796
After:  9802, 8558, 9630, 12418, 9654
Target: 9800, 8458, 9634, 12290, 9702

Author: bblanchon

src/ArduinoJson/Variant/VariantData.hpp

@@ -316,9 +316,18 @@ class VariantImpl {
 
   template <typename TAdaptedString>
   VariantData* getOrAddMember(TAdaptedString key) {
+    return getOrAddMember(key, data_, resources_);
+  }
+
+  template <typename TAdaptedString>
+  static VariantData* getOrAddMember(TAdaptedString key, VariantData* data,
+                                     ResourceManager* resources) {
     if (key.isNull())
       return nullptr;
-    auto obj = isNull() ? toObject() : asObject();
+    if (!data)
+      return nullptr;
+    auto obj = data->type == VariantType::Null ? toObject(data, resources)
+                                               : asObject(data, resources);
     return obj.getOrAddMember(key);
   }