drop table only if the table exists

Author: suketa

test/duckdb_test/appender_test.rb

@@ -11,7 +11,7 @@ def setup
     end
 
     def safe_drop_table
-      @con.execute("DROP TABLE #{table};")
+      @con.execute("DROP TABLE IF EXISTS #{table};")
     rescue DuckDB::Error
       # ignore DuckDB::Error
     end