Add get_first_non_empty and use it into Database to simplify a little bit

src/utils/get_first_non_empty.cpp

@@ -0,0 +1,11 @@
+#include <utils/get_first_non_empty.hpp>
+
+bool is_empty(const std::string& val)
+{
+  return val.empty();
+}
+
+bool is_empty(const int& val)
+{
+  return val == 0;
+}