fix the DuckDB::PreparedStatement initialize function.

Author: suketa

ext/duckdb/prepared_statement.c

@@ -81,6 +81,8 @@ VALUE rbduckdb_prepared_statement_new(duckdb_connection con, duckdb_extracted_st
 static VALUE duckdb_prepared_statement_initialize(VALUE self, VALUE con, VALUE query) {
     rubyDuckDBConnection *ctxcon;
     rubyDuckDBPreparedStatement *ctx;
+    duckdb_state state;
+    const char *error;
 
     if (!rb_obj_is_kind_of(con, cDuckDBConnection)) {
         rb_raise(rb_eTypeError, "1st argument should be instance of DackDB::Connection");
@@ -89,10 +91,20 @@ static VALUE duckdb_prepared_statement_initialize(VALUE self, VALUE con, VALUE q
     TypedData_Get_Struct(self, rubyDuckDBPreparedStatement, &prepared_statement_data_type, ctx);
     ctxcon = get_struct_connection(con);
 
-    if (duckdb_prepare(ctxcon->con, StringValuePtr(query), &(ctx->prepared_statement)) == DuckDBError) {
-        const char *error = duckdb_prepare_error(ctx->prepared_statement);
+    // Initialize to NULL before preparing
+    ctx->prepared_statement = NULL;
+
+    // Try to prepare the statement and get the state
+    state = duckdb_prepare(ctxcon->con, StringValuePtr(query), &(ctx->prepared_statement));
+
+    // Get error message before any exception might be thrown
+    error = duckdb_prepare_error(ctx->prepared_statement);
+
+    // If preparation failed, raise Ruby exception with the error message
+    if (state == DuckDBError) {
         rb_raise(eDuckDBError, "%s", error ? error : "Failed to prepare statement(Database connection closed?).");
     }
+
     return self;
 }