function silently changes the length of its return vector depending on tree characteristics

Description:

In R/treeProfile.R, the code that computes merchantable volume returns a 0-row data.table when the filter matches no rows. This causes downstream logic to fail because it expects a single-row summary with Value = 0.

treeprofiledata[HT_I %>=% stumpHeight & DIB_I_next %>=% UTOPDIB,
.(Name = "VOL_MER", Value = sum(VOL_I, na.rm = TRUE))]

When the filter returns zero rows, the result is an empty data.table.

Expected behavior:
Always return a single-row summary, even when no rows match the filter.

Suggested fix:
data.table(Name = "VOL_MER",
Value = sum(treeprofiledata[HT_I %>=% stumpHeight &
DIB_I_next %>=% UTOPDIB, VOL_I],
na.rm = TRUE))

This ensures:

sum() returns 0 when no rows match

The output is always a single-row data.table

Downstream code receives consistent structure

File reference
R/treeProfile.R
Local path: C:/FAIBBase/R/treeProfile.R

Open R/treeProfile.R and locate the merchantable-volume calculation using the HT_I, stumpHeight, DIB_I_next, and UTOPDIB filter. Check the result when no rows match, then verify that the calculation consistently returns one row with Name set to VOL_MER and Value set to 0, without breaking downstream logic.

Written by the indexing model from the issue text.