discard bbox with zero area

frontend/document/document.lua

@@ -165,7 +165,8 @@ This method returns pagesize if bbox is corrupted
 function Document:getUsedBBoxDimensions(pageno, zoom, rotation)
 	local bbox = self:getPageBBox(pageno)
 	local ubbox_dimen = nil
-	if bbox.x0 < 0 or bbox.y0 < 0 or bbox.x1 < 0 or bbox.y1 < 0 then
+	if (bbox.x0 < 0) or (bbox.y0 < 0) or (bbox.x1 < 0) or (bbox.y1 < 0)
+	or (bbox.x0 == bbox.x1) or (bbox.y0 == bbox.y1) then
 		-- if document's bbox info is corrupted, we use the page size
 		ubbox_dimen = self:getPageDimensions(pageno, zoom, rotation)
 	else