bug fixed during trying to store the converted object into db

modules/Bio/EnsEMBL/Utils/Converter/bio_ens_exon.pm

@@ -77,6 +77,9 @@ sub _initialize {
 
 sub _attach_supporting_feature {
     my ($self, $exon, $ens_exon) = @_;
+    unless($exon->has_tag('supporting_feature')){
+        return;
+    }
     my ($sf) = $exon->each_tag_value('supporting_feature');
     unless(defined $sf){
         $self->warn("no supporting feature is attached in exon");

modules/Bio/EnsEMBL/Utils/Converter/bio_ens_predictionGene.pm

@@ -53,14 +53,14 @@ use Bio::EnsEMBL::Utils::Converter::bio_ens;
 sub _initialize {
     my ($self, @args) = @_;
 
-    $self->SUPER::_initialize(@args);
-
     $self->{_predictionExonConverter} = new Bio::EnsEMBL::Utils::Converter(
-        -in => 'Bio::Tools::Prediction::Exon',
+        -in => 'Bio::SeqFeature::Gene::Exon',
         -out => 'Bio::EnsEMBL::Exon',
-        -contig => $self->contig
     );
-
+    $self->SUPER::_initialize(@args);
+    
+    $self->{_predictionExonConverter}->contig($self->contig);
+    $self->{_predictionExonConverter}->analysis($self->analysis);
 }
 
 sub _convert_single {