fix: add null-check before buf_ allocation in ProcessQueryImpl

[mukejane]

Fixes #2163

Root cause: ProcessQueryImpl unconditionally allocates computer.inner_computer_->buf_ without checking if it is already non-null. If SetQuery() is called more than once on the same Computer object, the previously allocated buffer is leaked.

Fix: Wrap the allocation in a null-check, matching the pattern already used in ScalarQuantizer:

// Before (leaks memory on repeated SetQuery calls):
try {
    computer.inner_computer_->buf_ =
        reinterpret_cast<uint8_t*>(this->allocator_->Allocate(this->query_code_size_));

// After (safe):
try {
    if (computer.inner_computer_->buf_ == nullptr) {
        computer.inner_computer_->buf_ =
            reinterpret_cast<uint8_t*>(this->allocator_->Allocate(this->query_code_size_));
    }

Also applies to the bad_alloc catch block — buf_ is now only set to nullptr when it was originally null, avoiding overwriting an existing allocation on rethrow.

[mergify]

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[gemini-code-assist]

Code Review

This pull request updates ProcessQueryImpl in transform_quantizer.h to only allocate memory for computer.inner_computer_->buf_ if it is currently null, avoiding unnecessary allocations. There are no review comments, and I have no feedback to provide.

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[mukejane]

Hi @antgroup/vsag — this PR fixes a null pointer bug in ProcessImplInner. Mergify is blocking merge because the "kind" label is missing. Could you please add kind/bug label so it can merge? Happy to help with anything else.

[wxyucs]

Hi @mukejane, thanks for your contribution! I added labels and triggered the CI Testing. Now, please wait for the testing.