fix build error

include/bctoolbox/logging.h

@@ -332,7 +332,7 @@ public:
 	friend pumpstream& operator<<(pumpstream& __os, std::ostream& (*pf)(std::ostream&));
 
 private:
-	std::ostringstream mOstringstream{};
+	std::ostringstream mOstringstream;
 	bool mIslogLevelEnabled = false;
 	const char* mDomain;
 	const BctbxLogLevel mLevel;