Check for root mount point before going ahead.

src/modules/partition/gui/PartitionViewStep.cpp

@@ -187,9 +187,15 @@ PartitionViewStep::isNextEnabled() const
         return m_choicePage->isNextEnabled();
 
     if ( m_erasePage && m_erasePage == m_widget->currentWidget() )
-        return m_erasePage->isNextEnabled(); //FIXME: also check for mount point
+    {
+        return m_erasePage->isNextEnabled() &&
+               m_core->hasRootMountPoint();
+    }
+
+    if ( m_manualPartitionPage && m_manualPartitionPage == m_widget->currentWidget() )
+        return m_core->hasRootMountPoint();
 
-    return m_core->hasRootMountPoint();
+    return false;
 }