JsonString: change default ownership to Copied

src/ArduinoJson/MsgPack/MsgPackSerializer.hpp

@@ -96,7 +96,7 @@ class MsgPackSerializer : public VariantDataVisitor<size_t> {
   }
 
   size_t visit(JsonString value) {
-    ARDUINOJSON_ASSERT(value != NULL);
+    ARDUINOJSON_ASSERT(!value.isNull());
 
     auto n = value.size();
 

src/ArduinoJson/Strings/JsonString.hpp

@@ -22,10 +22,10 @@ class JsonString {
 
   JsonString() : str_(nullptr, 0, true) {}
 
-  JsonString(const char* data, Ownership ownership = Linked)
+  JsonString(const char* data, Ownership ownership = Copied)
       : str_(data, data ? ::strlen(data) : 0, ownership == Linked) {}
 
-  JsonString(const char* data, size_t sz, Ownership ownership = Linked)
+  JsonString(const char* data, size_t sz, Ownership ownership = Copied)
       : str_(data, sz, ownership == Linked) {}
 
   // Returns a pointer to the characters.

src/ArduinoJson/Variant/ConverterImpl.hpp

@@ -178,7 +178,7 @@ struct Converter<JsonString> : private detail::VariantAttorney {
 
   static JsonString fromJson(JsonVariantConst src) {
     auto data = getData(src);
-    return data ? data->asString() : 0;
+    return data ? data->asString() : JsonString();
   }
 
   static bool checkJson(JsonVariantConst src) {

src/ArduinoJson/Variant/VariantData.hpp

@@ -64,7 +64,8 @@ class VariantData {
         return visit.visit(content_.asObject);
 
       case VariantType::LinkedString:
-        return visit.visit(JsonString(content_.asLinkedString));
+        return visit.visit(
+            JsonString(content_.asLinkedString, JsonString::Linked));
 
       case VariantType::OwnedString:
         return visit.visit(JsonString(content_.asOwnedString->data,