Server crash - Lua _deflua_make_partisans_callback()

[jwrober]

Describe the bug

[critical] freeciv21-server (../common/scriptcore/luascript.cpp:453) - T417: lua error:       stack index 2, expected number, received number: not a numeric type that fits exactly an integer (number maybe has significant decimals) (bad argument into 'int(int, int)')
stack traceback:
        [C]: in function 'random'
        data/default/default.lua:191: in function '_deflua_make_partisans_callback'

To Reproduce
Steps to reproduce the behavior:

1. Start a game, use a savegame or run an autogame to get up to partisans
2. Build a partisan
3. See error

Expected behavior
No server crash on the Lua callback

Screenshots
N/A

Platform and version (please complete the following information):

• OS: Linux (but assume its everywhere)
• Freeciv21 version: 3.0-beta3
• Ruleset/Longturn game (if applicable): classic

Additional context
None

[lmoureaux]

This line from default.lua looks weird:

  local partisans = random(0, 1 + (city.size + 1) / 2) + 1

The upper bound in the random() call will be fractional if city.size is even. We need to floor() it explicitly or disable the check in sol2.