[partition] Uncomment updateButtons()

- This was commented out to combat the crash in device->type()
 - I believe the crash was caused by double-deletion, which was
   fixed in 2092ec3c9a by not re-
   parenting an immutable copy of something.
 - Restore the button-fix, since we need that to keep the
   *create* button in-sync with the selected partition.

FIXES #1097

src/modules/partition/gui/PartitionPage.cpp

@@ -581,7 +581,7 @@ void
 PartitionPage::onPartitionModelReset()
 {
     m_ui->partitionTreeView->expandAll();
-    // updateButtons();
+    updateButtons();
     updateBootLoaderIndex();
 }