Starts to handle exceptions

tracim/tracim/controllers/content.py

             revision_id = file.revision_id
 
         file_path = content_api.get_one_revision_filepath(revision_id)
-        nb_page = preview_manager.get_nb_page(file_path=file_path)
+        nb_page = 0
+        try:
+            nb_page = preview_manager.get_nb_page(file_path=file_path)
+        except:
+            pass
         preview_urls = []
         for page in range(int(nb_page)):
             url_str = '/previews/{}/pages/{}?revision_id={}'

tracim/tracim/controllers/page.py

         else:
             file = content_api.get_one(file_id, self._item_type)
             file_path = content_api.get_one_revision_filepath(file.revision_id)
-        path = preview_manager.get_jpeg_preview(file_path=file_path,
-                                                page=page,
-                                                height=size,
-                                                width=size)
-        with open(path, 'rb') as large:
-            return large.read()
+        try:
+            path = preview_manager.get_jpeg_preview(file_path=file_path,
+                                                    page=page,
+                                                    height=size,
+                                                    width=size)
+            with open(path, 'rb') as large:
+                return large.read()
+        except:
+            pass
 
     @expose(content_type='image/jpeg')
     def high_quality(self,