Function kernel_block_index_get_by_height 

pub unsafe extern "C" fn kernel_block_index_get_by_height(
    context: *const kernel_Context,
    chainstate_manager: *mut kernel_ChainstateManager,
    block_height: c_int,
) -> *mut kernel_BlockIndex

@brief Retrieve a block index by its height in the currently active chain. Once retrieved there is no guarantee that it remains in the active chain.

@param[in] context Non-null. @param[in] chainstate_manager Non-null. @param[in] block_height Height in the chain of the to be retrieved block index. @return The block index at a certain height in the currently active chain, or null if the height is out of bounds.