fbdev: add missing shadowRemove in CloseScreen()

Fixes crash in CloseScreen().
Signed-off-by: Julien Cristau <jcristau@debian.org>
Tested-by: Cyril Brulebois <kibi@debian.org>

src/fbdev.c

@@ -917,6 +917,7 @@ FBDevCloseScreen(int scrnIndex, ScreenPtr pScreen)
 	fbdevHWRestore(pScrn);
 	fbdevHWUnmapVidmem(pScrn);
 	if (fPtr->shadow) {
+	    shadowRemove(pScreen, pScreen->GetScreenPixmap(pScreen));
 	    xfree(fPtr->shadow);
 	    fPtr->shadow = NULL;
 	}