[BUG]: buffer tank & soft start temperature correction

[sailor25462]

Describe the bug
The soft start function shows unexpected behavior when a buffer tank is installed and activated.
Instead of (temporarily) reducing the target water temperature, the set target is instantly increased.

To Reproduce
To reproduce the behavior, a buffer tank must be activated in the Panasonic control panel and heishamon board (Top 99).
Top 113 "Buffer_Tank_Delta" must be set to some value >0K, as the Panasonic system will increase the output temp by the set delta. Required sensors (buffer tank temp, heating circuit temp, outside temp) have to be set properly to make the Panasonic system accept the buffer tank and keep it enabled.
Check in the node red dashboard, that buffer tank shows "enabled".

Enable soft start and see the correction value turning "+$k" instead of "-$k".

Expected behavior
Without buffer tank being enable, soft start will reduce (temporarily) the target temperature. With the buffer tank being enabled, target temperature should still be reduced for startup.

Screenshots