Set Subtitle in Change Recording Metadata Search

After a metadata Search within the 'Edit Recording
Metadata' screen, the subtitle value is mistakenly
written to the Description field. Then that value
is usually immediately overwritten by the real
description value.

This code change fixes the problem by properly
writing to the Subtitle field.

Resolves #667

(cherry picked from commit fdf5b09)

mythtv/programs/mythfrontend/playbackbox.cpp

@@ -5472,7 +5472,7 @@ void RecMetadataEdit::QueryComplete(MetadataLookup *lookup)
     m_episodeSpin->SetValue(lookup->GetEpisode());
     if (!lookup->GetSubtitle().isEmpty())
     {
-        m_descriptionEdit->SetText(lookup->GetSubtitle());
+        m_subtitleEdit->SetText(lookup->GetSubtitle());
     }
     if (!lookup->GetDescription().isEmpty())
     {