Pre-RE SC_SUB_WEAPONPROPERTY bonus no longer working (i.e. from Magnum Break)

SC_SUB_WEAPONPROPERTY is supposed to add "a percent of a normal attack in another element" (cit. Skotlex, battle.c), but that no longer happens (in pre-renewal mode)

Steps to reproduce:
- Use a character with the Magnum Break skill in its skill tree (tested on a Knight with 50 STR, 99 DEX equipped with a Sword[3] - but anything else is fine).
- Attack a monster (tested on a Geographer - anything else is fine).
- Attack it and note the average damage.
- Cast Magnum Break
- Attack the same monster again, and note the damage difference.

Expected result:
- Post-Magnum Break damage should be higher (unless the chosen monster is completely immune to Fire property attacks) than the initial damage, thanks to the SC_SUB_WEAPONPROPERTY bonus (+20% Fire damage given by Magnum Break)

Actual result:
- Post-MB damage is lower than the initial damage.

Regression range (git bisect):[code=auto:0]There are only 'skip'ped commits left to test. The first bad commit could be any of: 0bcefa16b14cc32a98d00e8a783bcf252c7fa1a1 47d6f48fd0cdad697ab762701230ce6b5503edc1 7c31f8720d8bd47c5ef134fc8dbe3bee54424af7 e721aebea358e6c480d7788911eed82b84ef523f 267ceb503f1e8002959f0a5b7ea49de61d1d572c We cannot bisect more! [/code](sorry about that - those revisions can't be compiled in pre-renewal mode due to [url="http://herc.ws/board/tracker/issue-7346-battlec-error"]Bug #7346[/url] - real culprit should be either 7c31f8720d8bd47c5ef134fc8dbe3bee54424af7 or 267ceb503f1e8002959f0a5b7ea49de61d1d572c, the other ones seem unrelated)