Remove calls to isMaximized

Remove some calls to `isMaximized` where we already know that the sub
window is not maximized, i.e. where these calls would always return
`false`.

One adjustment would have resulted in a call to `setHidden(false)`. This
was changed to `setVisible(true)` to get rid of the double negation.

The other `false` would have gotten in an or statement and thus could be
removed completely.

src/gui/SubWindow.cpp

@@ -296,6 +296,9 @@ void SubWindow::adjustTitleBar()
 		return;
 	}
 
+	// The sub window is not maximized, i.e. the title must be shown
+	// as well as some buttons.
+
 	// Title adjustments
 	m_windowTitle->show();
 
@@ -327,12 +330,12 @@ void SubWindow::adjustTitleBar()
 		buttonBarWidth = buttonBarWidth + m_buttonSize.width() + buttonGap;
 		m_maximizeBtn->move( middleButtonPos );
 		m_restoreBtn->move( middleButtonPos );
-		m_maximizeBtn->setHidden( isMaximized() );
+		m_maximizeBtn->setVisible(true);
 	}
 
 	// we're keeping the restore button around if we open projects
 	// from older versions that have saved minimized windows
-	m_restoreBtn->setVisible( isMaximized() || isMinimized() );
+	m_restoreBtn->setVisible(isMinimized());
 	if( isMinimized() )
 	{
 		m_restoreBtn->move( m_maximizeBtn->isHidden() ?  middleButtonPos : leftButtonPos );