Fix complex packing decode crash on trailing padding bits

consume_bits would crash with a MatchError when the remaining
bitstring had fewer bits than the group width. Added a guard
clause to stop consuming when insufficient bits remain, matching
how wgrib2 handles trailing padding in packed data sections.

lib/microwaveprop/weather/grib2/complex_packing.ex

@@ -191,7 +191,7 @@ defmodule Microwaveprop.Weather.Grib2.ComplexPacking do
     end
   end
 
-  defp consume_bits(<<>>, _width, _gref, acc), do: acc
+  defp consume_bits(bits, width, _gref, acc) when bit_size(bits) < width, do: acc
 
   defp consume_bits(bits, width, gref, acc) do
     <<val::size(width)-unsigned-big, rest::bitstring>> = bits