This is a patch release for the 6.16 LTS line, collecting crash fixes, safety guards, and release-branch maintenance updates. GUI Fix SEGV in ImFontAtlas::AddFontFromMemoryCompressedTTF when null pointer is passed as compressed font data: #2516 Fix ImGui::ColorPicker3/ColorPicker4 crashes when called without an active ImGui context or window: #2668 Use modern ImGui modifier key names in the OSG ImGui handler for newer ImGui builds. (#2526) Constraint Ignore malformed contacts with null collision objects instead of dereferencing them while creating ContactConstraint: #2669 Hide bundled ImGui internal formatting helpers from shared library exports: #2671 Parsers Return safe defaults from XML attribute helpers when callers pass a null element: #2678 Utils Reject mismatched C3D frame or marker counts in saveC3DFile() instead of indexing past point data: #2681 Common Fix iterator invalidation in Subject/Observer notification loops that caused non-deterministic SEGFAULT on macOS arm64 Debug builds Fix spdlog/fmt 12 builds by treating DART logging format parameters as runtime format strings. (#2540, #2538) Fix PoolAllocator leaking old memory block tables when the table grows. (#2646) Simulation Reject NaN, infinite, zero, and negative World::setTimeStep() values to prevent invalid timesteps from reaching the ODE LCP solver. (#2532, #2531) Tooling and Docs Improve FreeBSD VM CI startup resilience with a release image URL, fallback image downloads, a longer SSH readiness window, fresh VM container startup, KVM group propagation, retry handling, and startup diagnostics. (#2532) Remove duplicate .gitignore entries. (#2735) Update Pixi lockfiles for current conda-forge package builds. (#2766, #2780)