Partition: don't set text if button doesn't exist

src/modules/partition/gui/ChoicePage.cpp

@@ -140,8 +140,11 @@ ChoicePage::retranslate()
     m_previewBeforeLabel->setText( tr( "Current:" ) );
     m_previewAfterLabel->setText( tr( "After:" ) );
 
+    if ( m_somethingElseButton )
+    {
         m_somethingElseButton->setText( tr( "<strong>Manual partitioning</strong><br/>"
                                             "You can create or resize partitions yourself." ) );
+    }
     updateSwapChoicesTr( m_eraseSwapChoiceComboBox );
 }