pscl crashes with string variable

[strengejacke]

Fixes #1132

[gemini-code-assist]

Summary of Changes

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This pull request delivers a crucial bug fix for the parameters package, resolving a crash that previously occurred when processing pscl models (zeroinfl and hurdle) that included string variables. The underlying issue stemmed from an attempt to manipulate pretty_labels when they were NULL. The fix involves a precise adjustment to the code's logic, ensuring that such operations are only performed when pretty_labels are valid. A new, targeted test case has been introduced to confirm the fix and prevent future regressions.

Highlights

• Bug Fix: Resolved a crash in the parameters package that occurred when pscl models (specifically zeroinfl and hurdle models) were fitted using string variables. This addresses the issue reported in #1132.
• Code Refinement: Refactored the format_parameters.parameters_model function in R/format_parameters.R by relocating the logic responsible for prefixing pretty_labels with 'count_' and 'zero_' for pscl models. This logic is now correctly nested within a check to ensure pretty_labels is not NULL, preventing operations on non-existent objects.
• Test Coverage: Added a new testthat test case in tests/testthat/test-pretty_names.R to specifically validate that pscl::zeroinfl models, when used with character variables, no longer cause a crash and produce the expected output dimensions.
• Version Update: Incremented the package version in DESCRIPTION from 0.26.0.15 to 0.26.0.16.

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[gemini-code-assist]

Code Review

The pull request addresses a crash issue with string variables in the pscl package. The fix involves relocating a block of code related to handling 'count_' and 'zero_' prefixes for models from pscl within a conditional block that checks for the existence of pretty labels. Additionally, a test case has been added to ensure that the code doesn't crash when pretty labels are NULL.