Fix problem with clippy:manual_unwrap_or_default

[wcampbell0x2a]

• Fix bugged trigger in darling over new stable clippy lint. This is the same fix that serde_with used.

See https://github.com/rust-lang/rust-clippy/issues/12643

[github-actions[bot]]

Benchmark for 37a7d07

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| Test | Base | PR | % | |------|--------------|------------------|---| | deku_read_bits | 1245.8±14.56ns | **1227.9±13.30ns** | **-1.44%** | | deku_read_byte | 3.5±0.04ns | **3.3±0.11ns** | **-5.71%** | | deku_read_enum | 2.6±0.08ns | **2.5±0.05ns** | **-3.85%** | | deku_read_vec | 33.4±0.52ns | 33.4±0.47ns | 0.00% | | deku_write_bits | 166.3±5.73ns | 166.7±4.77ns | +0.24% | | deku_write_byte | 22.7±0.32ns | 22.7±0.46ns | 0.00% | | deku_write_enum | 21.4±0.41ns | 21.1±0.35ns | -1.40% | | deku_write_vec | 416.4±4.06ns | **401.4±6.46ns** | **-3.60%** |