Null-safe checks

Make null/empty handling explicit and safe—so empty values don’t break logic or even generate invalid syntax, and raw null-pointer checks are replaced with semantic, invariant-based checks.

Guidelines: 1) Avoid “empty variable” syntax bugs (CMake): quote variables in comparisons.

• Bad: elseif(${CMAKE_CXX_COMPILER_ID} STREQUAL "Clang") (breaks if the variable expands to empty)
• Good: elseif("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")

2) Prefer semantic checks over raw pointer null checks (C++ containers/tensors):

• Replace if (ptr != NULL) with if (!obj.empty()) or equivalent invariants when available.
• Example pattern: if (!_bias.empty()) { /* use bias */ } else { /* no bias */ }

3) Don’t over-defend against null in operations that are already null-safe:

• delete NULL; is safe—unnecessary if (ptr) delete ptr; can be removed for clarity.

4) For null-terminated byte strings, ensure the correct terminator behavior:

• When constructing/copying C-strings into custom buffers, allocate/copy consistently so the destination is properly null-terminated (e.g., consider whether you need len + 1 and whether you copy len+1).

Applying these rules reduces crashes, undefined behavior, and correctness issues caused by missing/empty/null values.