dashdemux: Always create the adapter

Worst case it will be empty. This fixes a crash when the base class
calls data_received() when the stream is neither is_isobmff or
has_isoff_ondemand_profile.

https://bugzilla.gnome.org/show_bug.cgi?id=796745
diff --git a/ext/dash/gstdashdemux.c b/ext/dash/gstdashdemux.c
index b2b6b4b..d011f23 100644
--- a/ext/dash/gstdashdemux.c
+++ b/ext/dash/gstdashdemux.c
@@ -846,9 +846,7 @@
     stream->is_isobmff = gst_structure_has_name (s, "video/quicktime")
         || gst_structure_has_name (s, "audio/x-m4a");
     stream->first_sync_sample_always_after_moof = TRUE;
-    if (stream->is_isobmff
-        || gst_mpd_client_has_isoff_ondemand_profile (demux->client))
-      stream->adapter = gst_adapter_new ();
+    stream->adapter = gst_adapter_new ();
     gst_adaptive_demux_stream_set_caps (GST_ADAPTIVE_DEMUX_STREAM_CAST (stream),
         caps);
     if (tags)