Media: Fix reference to ambiguous column

"Failed to compile/prepare request [SELECT COUNT(DISTINCT id_media ) FROM Media m  LEFT JOIN File f ON m.id_media = f.media_id  WHERE folder_id = ?]: ambiguous column name: folder_id(1)"

src/Media.cpp

@@ -953,10 +953,10 @@ Query<IMedia> Media::fromFolderId( MediaLibraryPtr ml, IMedia::Type type,
     // manipulated when the device is not present
     std::string req = "FROM " + Table::Name +  " m ";
     req += addRequestJoin( params, false, false );
-    req += " WHERE folder_id = ?";
+    req += " WHERE m.folder_id = ?";
     if ( type != Type::Unknown )
     {
-        req += " AND type = ?";
+        req += " AND m.type = ?";
         return make_query<Media, IMedia>( ml, "*", req, sortRequest( params ),
                                           folderId, type );
     }

test/unittest/FolderTests.cpp

@@ -646,6 +646,16 @@ TEST_F( FoldersNoDiscover, ListWithMedia )
     mediaQuery = folders[0]->media( IMedia::Type::Unknown, nullptr );
     ASSERT_EQ( 2u, mediaQuery->count() );
     ASSERT_EQ( 2u, mediaQuery->all().size() );
+
+    // Now try sorting by last modified date, which was causing a crash
+    params.sort = SortingCriteria::LastModificationDate;
+    mediaQuery = folders[0]->media( IMedia::Type::Unknown, &params );
+    ASSERT_EQ( 2u, mediaQuery->count() );
+    ASSERT_EQ( 2u, mediaQuery->all().size() );
+
+    mediaQuery = folders[0]->media( IMedia::Type::Audio, &params );
+    ASSERT_EQ( 1u, mediaQuery->count() );
+    ASSERT_EQ( 1u, mediaQuery->all().size() );
 }
 
 TEST_F( FoldersNoDiscover, ListSubFolders )