[BUG] FOLLOWING keyword throws stoi

[drabastomek]

Describe the bug Using the FOLLOWING keyword in window functions throws stoi error.

Steps/Code to reproduce bug

import blazingsql as bsql
import cudf

df = cudf.DataFrame({
    'np_int8': np.int8(np.arange(-5, 6))
    , 'category': ['A', 'A', 'A'
    , 'B', 'B', 'B'
    , 'C', 'C', 'C'
    , 'D', None]
})
bc = bsql.BlazingContext()
bc.create_table('df_table', df)

bc.sql('''
    SELECT category, SUM(np_int8) OVER (PARTITION BY category ORDER BY np_int8 NULLS FIRST ROWS 2 FOLLOWING)
    FROM df_table
    ORDER BY category DESC
''')

The PRECEDING keyword works as intended.

Expected behavior Not throw an error and produce proper result.

Environment overview (please complete the following information)

• Environment location: Bare-metal
• Method of BlazingSQL install: from source
• BlazingSQL Version: 'ba4a97a3ce3f1c733a135bf88518f2f67b12b519'

[drabastomek]

cc: @williamBlazing