Don't allow 'give health 0' or even less.

Giving the player < -1 health and increasing it to something
above 0 without closing the console breaks the player state.

src/g_cmds.c

@@ -229,6 +229,7 @@ Cmd_Give_f(edict_t *ent)
 		if (gi.argc() == 3)
 		{
 			ent->health = atoi(gi.argv(2));
+		    ent->health = ent->health < 1 ? 1 : ent->health; 
 		}
 		else
 		{