From 90c38e2d0d162a7dd10af0ff9f169cb9dce96d06 Mon Sep 17 00:00:00 2001
From: NiLuJe <ninuje@gmail.com>
Date: Tue, 18 May 2021 18:20:34 +0200
Subject: [PATCH] ReadHistory: nil guard a Document instance access

We're now more careful about this, so, I suppose weird timings may mean
we might be trying to access a nil here.

Fix #7706

Guard a few other similar constructs
---
 frontend/apps/filemanager/filemanagerhistory.lua | 2 +-
 frontend/readhistory.lua                         | 2 +-
 frontend/ui/screensaver.lua                      | 8 ++++----
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/frontend/apps/filemanager/filemanagerhistory.lua b/frontend/apps/filemanager/filemanagerhistory.lua
index f71a11f6d..1af9aa76f 100644
--- a/frontend/apps/filemanager/filemanagerhistory.lua
+++ b/frontend/apps/filemanager/filemanagerhistory.lua
@@ -44,7 +44,7 @@ end
 
 function FileManagerHistory:onMenuHold(item)
     local readerui_instance = require("apps/reader/readerui"):_getRunningInstance()
-    local currently_opened_file = readerui_instance and readerui_instance.document.file
+    local currently_opened_file = readerui_instance and readerui_instance.document and readerui_instance.document.file
     self.histfile_dialog = nil
     local buttons = {
         {
diff --git a/frontend/readhistory.lua b/frontend/readhistory.lua
index 9cb0f326f..8a16226c2 100644
--- a/frontend/readhistory.lua
+++ b/frontend/readhistory.lua
@@ -30,7 +30,7 @@ local function buildEntry(input_time, input_file)
         -- mandatory = file_exists and util.getFriendlySize(lfs.attributes(input_file, "size") or 0),
         mandatory_func = function() -- Show the last read time (rather than file size)
             local readerui_instance = require("apps/reader/readerui"):_getRunningInstance()
-            local currently_opened_file = readerui_instance and readerui_instance.document.file
+            local currently_opened_file = readerui_instance and readerui_instance.document and readerui_instance.document.file
             local last_read_ts
             if file_path == currently_opened_file then
                 -- Don't use the sidecar file date which is updated regularly while
diff --git a/frontend/ui/screensaver.lua b/frontend/ui/screensaver.lua
index 10e17dd5c..2b0d0639e 100644
--- a/frontend/ui/screensaver.lua
+++ b/frontend/ui/screensaver.lua
@@ -118,7 +118,7 @@ local function expandSpecial(message, fallback)
 
     local ReaderUI = require("apps/reader/readerui")
     local ui = ReaderUI:_getRunningInstance()
-    if ui then
+    if ui and ui.document then
         -- If we have a ReaderUI instance, use it.
         local doc = ui.document
         currentpage = ui.view.state.page or currentpage
@@ -303,7 +303,7 @@ end
 function Screensaver:isExcluded()
     local ReaderUI = require("apps/reader/readerui")
     local ui = ReaderUI:_getRunningInstance()
-    if ui then
+    if ui and ui.doc_settings then
         local doc_settings = ui.doc_settings
         return doc_settings:isTrue("exclude_screensaver")
     else
@@ -415,7 +415,7 @@ function Screensaver:setup(event, fallback_message)
         local excluded
         if DocSettings:hasSidecarFile(self.lastfile) then
             local doc_settings
-            if ui then
+            if ui and ui.doc_settings then
                 doc_settings = ui.doc_settings
             else
                 doc_settings = DocSettings:open(self.lastfile)
@@ -427,7 +427,7 @@ function Screensaver:setup(event, fallback_message)
         end
         if not excluded then
             if self.lastfile and lfs.attributes(self.lastfile, "mode") == "file" then
-                if ui then
+                if ui and ui.document then
                     local doc = ui.document
                     self.image = doc:getCoverPageImage()
                 else