base: add a default src_event virtual method
base: add a default src_event virtual method

... so that not all event (including seeks) will get lost.

Signed-off-by: Mark Nauwelaerts <b7a9d5e0b6d7b100d27ef2a8e80c5c1c14a8de12@collabora.co.uk>
Signed-off-by: Felipe Contreras <de77a8b9cd239b204c19c52ed62e48ab47243362@nokia.com>

community-ssu/gst-dsp,community-ssu/gst-dsp,felipec/gst-dsp,felipec/gst-dsp,community-ssu/gst-dsp