All I can do for you is point you at the probably right address in your firmware. Your firmware doesn't have this two funcitions named like sx220, but seems like in both firmwares are located in similar places. This looks also to be like a hardware defect table but I don't know how it works.
The address is 0x27B4+0x34 . If 1 is enabled, 0 disabled. On my camera the lens error is always enabled, if I disable it nothing happens and returns back to enabled when I turn the camera off/on.
ixus 105.100d
ROM:FFC5CE6C sub_FFC5CE6C ; CODE XREF: sub_FFC5CF30+68p
ROM:FFC5CE6C ; sub_FFD151F4+44p ...
ROM:FFC5CE6C LDR R1, =0x27B4 <-------- this
ROM:FFC5CE70 STMFD SP!, {R4,LR}
ROM:FFC5CE74 LDR R2, [R1,#0x34] <-------- and this
ROM:FFC5CE78 CMP R2, #0
ROM:FFC5CE7C LDMNEFD SP!, {R4,PC}
ROM:FFC5CE80 MOV R2, #1
ROM:FFC5CE84 STR R2, [R1,#0x34]
ROM:FFC5CE88 AND R1, R0, #0xFF00
ROM:FFC5CE8C CMP R1, #0x100
ROM:FFC5CE90 BEQ loc_FFC5CEC8
ROM:FFC5CE94 CMP R1, #0x200
ROM:FFC5CE98 BEQ loc_FFC5CED8
ROM:FFC5CE9C CMP R1, #0x400
ROM:FFC5CEA0 LDRNE R1, =0xB2E
ROM:FFC5CEA4 LDRNE R0, =aIsdriver_c
ROM:FFC5CEA8 LDMNEFD SP!, {R4,LR}