libcamera: device_enumerator_udev: Remove devnum from dependency map

Previously, after `addV4L2Device()` had seen all dependecies, it would
remove the `MediaDeviceDeps` object from the `pending_` list, which
would result in it being destroyed. However, there would still be
(dangling) pointers to this object in `devMap_` that were added in
`addUdevDevice()` (line 103). So remove the entry with the given devnum
when it is removed from the corresponding `MediaDeviceDeps` object.

Signed-off-by: Barnabás Pőcze <pobrn@protonmail.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/libcamera/device_enumerator_udev.cpp

@@ -315,6 +315,7 @@ int DeviceEnumeratorUdev::addV4L2Device(dev_t devnum)
 	 * enumerator.
 	 */
 	deps->deps_.erase(devnum);
+	devMap_.erase(it);
 
 	if (deps->deps_.empty()) {
 		LOG(DeviceEnumerator, Debug)