Possible misuse of sqlite3_column_table_name et al

[ericsink]

Original issue at ericsink/SQLitePCL.raw#479

I am concerned about possible problems with the calls to the SQLite column metadata functions (sqlite3_column_database_name, sqlite3_column_table_name, sqlite3_column_origin_name) in this area of the code:

efcore/src/Microsoft.Data.Sqlite.Core/SqliteDataRecord.cs

Lines 315 to 343 in f742668

	var databaseName = sqlite3_column_database_name(Handle, i).utf8_to_string();
	if (databaseName != blobDatabaseName)
	{
	continue;
	}
	var tableName = sqlite3_column_table_name(Handle, i).utf8_to_string();
	if (tableName != blobTableName)
	{
	continue;
	}
	var columnName = sqlite3_column_origin_name(Handle, i).utf8_to_string();
	if (columnName == "rowid")
	{
	_rowidOrdinal = i;
	break;
	}
	var rc = sqlite3_table_column_metadata(
	_connection.Handle,
	databaseName,
	tableName,
	columnName,
	out var dataType,
	out var collSeq,
	out var notNull,
	out var primaryKey,
	out var autoInc);

The docs:

https://www.sqlite.org/c3ref/column_database_name.html

say that these functions return NULL when the origin is an expression ... not a column value. And looking at the code, it seems possible that those NULLs would find their way into the call to sqlite3_table_column_metadata. Which would explain the behavior seen in the original issue.