Fix print() for Wiener/RT-choice estimates without a Component column

[Copilot]

For is_wiener / is_rtchoice models, every print() method went to .print_drift_diffusion(), which splits the table by Component. Only response predictions have that column, so printing estimates of a distributional parameter (predict = "mu", "bs") failed. .print_drift_diffusion() also failed when only one component was left, e.g. after subsetting.

m <- brm(bf(rt | dec(resp) ~ x), data = d, family = wiener())

estimate_means(m, by = "x", predict = "mu")        # previously: Error in `$<-.data.frame`
estimate_contrasts(m, contrast = "x", predict = "mu")
head(estimate_prediction(m), 2)                    # previously: Error in `x[[i]] <- value`

Changes

• print.estimate_contrasts() (R/print.R)
  • The drift-diffusion branch now also requires a Component column. Tables without one use the regular formatting path.
  • The seven print methods that alias this function are fixed too.
• .print_drift_diffusion() (R/print.R)
  • Dropping the other component's columns is skipped when setdiff(names(out), i) is empty. With a single component, out[[i]][[character(0)]] <- NULL threw an error.

No tests, NEWS.md entry or version bump are included yet.

• Fixes print() fails for estimate_means() / estimate_contrasts() on Wiener and RT-choice models #680

[Copilot]

🟡 Changes recommended

Regression tests are missing for both corrected printing failures.

1 open finding

• Add regression tests for printer guard cases · New

What changed in this PR

Fixes printing failures for Wiener and RT-choice estimates in the shared printer, addressing #680.

Changes:

• Uses regular formatting when Component is absent.
• Avoids invalid column removal when only one component remains.

File	Description
R/​print.R	Guards component-specific formatting and single-component column removal.

🧠 Review effort: Balanced

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