[gnome-documents] lokview: be robust to LibreOfficeKit not being available

[Cosimo Cecchi <cosimoc src gnome org>]

commit cc19ed47cc81a59a379edefcc0e37c61803f51b4
Author: Cosimo Cecchi <cosimoc gnome org>
Date:   Mon Sep 2 12:02:51 2019 -0700

    lokview: be robust to LibreOfficeKit not being available
    
    When LibreOfficeKit is not available, we still create a LOKView
    preview.
    
    We then need to check whether the internal LOKDocView exists before
    calling a method on it, or we will trigger an exception that will
    prevent the regular error page from kicking in.
    
    Fixes https://gitlab.gnome.org/GNOME/gnome-documents/issues/37

 src/lokview.js | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)
---
diff --git a/src/lokview.js b/src/lokview.js
index d0d3afa6..f92467a2 100644
--- a/src/lokview.js
+++ b/src/lokview.js
@@ -210,7 +210,7 @@ var LOKView = GObject.registerClass(class LOKView extends Preview.Preview {
     }
 
     goPrev() {
-        let currentPart = this._lokview.get_part();
+        let currentPart = this.page;
         currentPart -= 1;
         if (currentPart < 0)
             return;
@@ -220,8 +220,8 @@ var LOKView = GObject.registerClass(class LOKView extends Preview.Preview {
     }
 
     goNext() {
-        let totalParts  = this._lokview.get_parts();
-        let currentPart = this._lokview.get_part();
+        let totalParts  = this.numPages;
+        let currentPart = this.page;
         currentPart += 1;
         if (currentPart > totalParts)
             return;
@@ -235,10 +235,10 @@ var LOKView = GObject.registerClass(class LOKView extends Preview.Preview {
     }
 
     get page() {
-        return this._lokview.get_part();
+        return this._lokview ? this._lokview.get_part() : 0;
     }
 
     get numPages() {
-        return this._lokview.get_parts();
+        return this._lokview ? this._lokview.get_parts() : 0;
     }
 });