change suggested by Matthieu to avoid crashing if the temp_directory has...

change suggested by Matthieu to avoid crashing if the temp_directory has already been deleted by Runnable

modules/Bio/EnsEMBL/Hive/Process.pm

@@ -557,7 +557,7 @@ sub cleanup_worker_temp_directory {
         # TODO: simplify $holding_object=$self when -compile_module_once becomes the only option:
     my $holding_object = $self->worker ? $self->worker : $self;
 
-    if($holding_object->{'_tmp_dir'}) {
+    if($holding_object->{'_tmp_dir'} and (-e $holding_object->{'_tmp_dir'}) ) {
         my $cmd = "rm -r ". $holding_object->{'_tmp_dir'};
         system($cmd);
     }

modules/Bio/EnsEMBL/Hive/Worker.pm

@@ -456,7 +456,7 @@ sub toString {
 
 sub cleanup_worker_process_temp_directory {
   my $self = shift;
-  if($self->{'_tmp_dir'}) {
+  if($self->{'_tmp_dir'} and (-e $self->{'_tmp_dir'}) ) {
     my $cmd = "rm -r ". $self->{'_tmp_dir'};
     system($cmd);
   }