[build] extension_extra should include empty lists for all values that are accessed
[build] extension_extra should include empty lists for all values that are accessed

mcpv/PyAV,xxr3376/PyAV,markreidvfx/PyAV,PyAV-Org/PyAV,mcpv/PyAV,markreidvfx/PyAV,PyAV-Org/PyAV,mikeboers/PyAV,pupil-labs/PyAV,pupil-labs/PyAV,pupil-labs/PyAV,xxr3376/PyAV,mikeboers/PyAV,markreidvfx/PyAV,mcpv/PyAV,xxr3376/PyAV,pupil-labs/PyAV