MSVC warning and fix #2627

Author: glebm

src/ast.cpp

@@ -1561,7 +1561,7 @@ namespace Sass {
   {
     if (String_Schema_Obj schema = Cast<String_Schema>(contents())) {
       if (schema->length() == 0) return false;
-      return Cast<Parent_Reference>(schema->at(0));
+      return Cast<Parent_Reference>(schema->at(0)) != nullptr;
     }
     return false;
   }

src/operation.hpp

@@ -200,7 +200,7 @@ namespace Sass {
     {
       std::string msg(typeid(*this).name());
       msg += ": CRTP not implemented for ";
-      throw std::runtime_error(msg + typeid(*x).name());
+      throw std::runtime_error(msg + typeid(x).name());
     }
 
   };