[FIX] Guard against NULL timing context when reporting decoder statistics

[hridyasadanand]

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Summary

This PR adds a defensive NULL check for dec_ctx->timing in the decoder reporting loop at the end of start_ccx().

Under certain execution paths, decoder contexts present in ctx->dec_ctx_head may not have an associated timing context. The current code unconditionally dereferences dec_ctx->timing, which can lead to undefined behavior or crashes.

This change safely skips such decoder entries during reporting.

Problem Description

The reporting loop in start_ccx() assumes that every decoder in ctx->dec_ctx_head has a valid timing structure and unconditionally accesses timing fields.

While decoders created via init_cc_decode() always initialize timing, decoder contexts created via copy_decoder_context() explicitly set timing = NULL. These copied decoder contexts may still be present in dec_ctx_head.

As a result, dec_ctx->timing is not guaranteed to be non-NULL at this point.

Fix

Add a simple guard before accessing timing fields:

if (!dec_ctx->timing)
    continue;