Maybe Unitiailized Variable Warning on gcc 8.2

Created by: furkanusta

Because of the name of the project I wasn't sure the target platform is supposed to be an Arduino but when I comment out -Werror the library builds fine and passes the tests. That is why, I've opened this issue.

I am on x86_64, Fedora 29. Using g++ 8.2

And these are the warnings I got

../test/JsonVariant/subscript.cpp: In function ‘void ____C_A_T_C_H____T_E_S_T____0()’: ../test/JsonVariant/subscript.cpp:71:17: warning: ‘var.ArduinoJson::JsonVariant::_content.ArduinoJson::Internals::JsonVariantContent::asArray’ may be used uninitialized in this function [-Wmaybe-uninitialized] JsonVariant var = _jsonBuffer.parseArray("[{}]");

../test/JsonVariant/subscript.cpp:67:42: warning: ‘var.ArduinoJson::JsonVariant::_content.ArduinoJson::Internals::JsonVariantContent::asArray’ may be used uninitialized in this function [-Wmaybe-uninitialized] REQUIRE(std::string("world") == var[0]);

../test/JsonVariant/subscript.cpp:19:55: warning: ‘var.ArduinoJson::JsonVariant::_content.ArduinoJson::Internals::JsonVariantContent::asArray’ may be used uninitialized in this function [-Wmaybe-uninitialized] REQUIRE(std::string("element at index 0") == var[0]);