fix: read stats crashes pdf/djvu documents

frontend/apps/reader/modules/readerfooter.lua

@@ -230,7 +230,12 @@ function ReaderFooter:getProgressPercentage()
 end
 
 function ReaderFooter:getBookTimeToRead()
-    local current_page = self.view.document:getCurrentPage()
+    local current_page
+    if self.view.document.info.has_pages then
+        current_page = self.ui.paging.current_page
+    else
+        current_page = self.view.document:getCurrentPage()
+    end
     return self:getDataFromStatistics("TB: ", self.pages - current_page)
 end
 

spec/unit/readerfooter_spec.lua

@@ -0,0 +1,30 @@
+require("commonrequire")
+local DocumentRegistry = require("document/documentregistry")
+local ReaderUI = require("apps/reader/readerui")
+local DEBUG = require("dbg")
+
+describe("Readerfooter module", function()
+    it("should setup footer for epub without error", function()
+        local sample_epub = "spec/front/unit/data/juliet.epub"
+        local readerui = ReaderUI:new{
+            document = DocumentRegistry:openDocument(sample_epub),
+        }
+        readerui.view.footer.settings.all_at_once = true
+        readerui.view.footer:updateFooterPage()
+        timeinfo = readerui.view.footer:getTimeInfo()
+        assert.are.same('B:0% | '..timeinfo..' | => 0 | R:100% | TB: 00:00 | TC: 00:00',
+                        readerui.view.footer.progress_text.text)
+    end)
+
+    it("should setup footer for pdf without error", function()
+        local sample_pdf = "spec/front/unit/data/2col.pdf"
+        local readerui = ReaderUI:new{
+            document = DocumentRegistry:openDocument(sample_pdf),
+        }
+        readerui.view.footer.settings.all_at_once = true
+        readerui.view.footer:updateFooterPage()
+        timeinfo = readerui.view.footer:getTimeInfo()
+        assert.are.same('B:0% | '..timeinfo..' | => 1 | R:50% | TB: na | TC: na',
+                        readerui.view.footer.progress_text.text)
+    end)
+end)