[clang-tidy] Fix if-constexpr false-positive in readability-misleading-indentation

When  depend on template parameter,
compiler can use NullStmt instead of CompoundStmt.
This causes issues as we losing information about
end location of that Stmt. To avoid this issue
check now ignores ifStmt with NullStmt on true-branch.

Fixes: https://github.com/llvm/llvm-project/issues/61435

Reviewed By: carlosgalvezp

Differential Revision: https://reviews.llvm.org/D146887