Fixing null pointer dereference.

sql/connection.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SQL_CONNECTION_H_
 #define SQL_CONNECTION_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 352 matching lines @@
   class SQL_EXPORT StatementRef : public base::RefCounted<StatementRef> {
    public:
     // Default constructor initializes to an invalid statement.
     StatementRef();
     explicit StatementRef(sqlite3_stmt* stmt);
     StatementRef(Connection* connection, sqlite3_stmt* stmt);
 
     // When true, the statement can be used.
     bool is_valid() const { return !!stmt_; }
 
-    // If we've not been linked to a connection, this will be NULL. Guaranteed
-    // non-NULL when is_valid().
+    // If we've not been linked to a connection, this will be NULL.
+    // TODO(shess): connection_ can be NULL in case of GetUntrackedStatement(),
+    // which prevents Statement::OnError() from forwarding errors.
     Connection* connection() const { return connection_; }
 
     // Returns the sqlite statement if any. If the statement is not active,
     // this will return NULL.
     sqlite3_stmt* stmt() const { return stmt_; }
 
     // Destroys the compiled statement and marks it NULL. The statement will
     // no longer be active.
     void Close();
 
@@ skipping 81 matching lines @@
 
   // Auxiliary error-code histogram.
   std::string error_histogram_name_;
 
   DISALLOW_COPY_AND_ASSIGN(Connection);
 };
 
 }  // namespace sql
 
 #endif  // SQL_CONNECTION_H_