Cs 1.6 Glitch crashes game.

Well when i was playing cs 1.6 (because its been 1 year now that i didnt play cs 1.6 now i downloaded it) it crashed because of a freakin glitch i called multi pick-up,

its like like this when i have m4a1 and i stand into a mac-10 i pick-up mac-10 w/o dropping m4a1 then the game crashed.

the glitch mostly occurs on many weapons map like fy_iceworld and fy_etc.

How can you pick up a primary weapon while holding a primary weapon?