Fix double free crash

[bmatherly]

If the caller frees the returned object (which they should), then a double free error will occur because the encapsulated mlt_profile will be freed by the Profile and by the origional service that owned it.

[ddennedy]

Where is this other free? Services do not own the profile.

[ddennedy]

Mlt::FilteredProducer::detach() constructs a Profile whose destructor frees the mlt_profile via mlt_profile_close() but the Mlt::Profile is not required due to a Mlt::Producer constructor that takes a mlt_profile:

--- src/mlt++/MltFilteredProducer.cpp
+++ src/mlt++/MltFilteredProducer.cpp
@@ -66,8 +66,7 @@ int FilteredProducer::detach(Filter &filter)
             Service *consumer = it->consumer();
             if (consumer->is_valid())
                 consumer->connect_producer(*producer);
-            Profile p(get_profile());
-            Producer dummy(p, "colour");
+            Producer dummy(get_profile(), "colour");
             dummy.connect_producer(*it);
             if (last->get_service() == it->get_service()) {
                 delete last;

[bmatherly]

Where is this other free? Services do not own the profile.

Presumably, whoever owns the mlt_profile that was passed to the constructor will either still try to use it (access freed memory) or free it (double free).

I wonder if we should deprecate Service::profile() to discourage its use. Mlt::Properties does not follow the same pattern as other Mlt classes. Other classes that take an mlt_properties based object in their constructor work properly because mlt_properties are reference counted.