Purge some return undef;

modules/Bio/EnsEMBL/DBSQL/BaseAdaptor.pm

@@ -674,7 +674,7 @@ sub _uncached_fetch_by_dbID{
   #Should only be one
   my ($feat) = @{$self->generic_fetch($constraint)};
 
-  return undef if(!$feat);
+  return if(!$feat);
 
   return $feat;
 }
@@ -1151,7 +1151,7 @@ sub _logic_name_to_constraint {
   my $an = $aa->fetch_by_logic_name($logic_name);
 
   if ( !defined($an) ) {
-    return undef;
+    return;
   }
 
   my $an_id = $an->dbID();

modules/Bio/EnsEMBL/DBSQL/SliceAdaptor.pm

@@ -322,7 +322,7 @@ sub fetch_by_region {
       $syn_sql_sth->finish;
 
 
-      if ($no_fuzz) { return undef }
+      if ($no_fuzz) { return; }
 
       # Do fuzzy matching, assuming that we are just missing a version
       # on the end of the seq_region name.
@@ -398,7 +398,7 @@ sub fetch_by_region {
       $cs = $high_cs;
 
       # return if we did not find any appropriate match:
-      if ( !defined($high_ver) ) { return undef }
+      if ( !defined($high_ver) ) { return; }
 
     } else {