Revert "Don't crash on manual lookup from filemanager either"

This reverts commit b6b4ead.

This is not actually necessary now because there should be no situation
where there's no document available

ankinote.lua

@@ -42,9 +42,6 @@ end
 -- Create metadata string about the document the word came from.
 -- ]]
 function AnkiNote:get_metadata()
-    if not self.ui.document then
-        return
-    end
     local meta = self.ui.document._anki_metadata
     return string.format("%s - %s (%d/%d)", meta.author, meta.title, meta:current_page(), meta.pages)
 end
@@ -126,9 +123,6 @@ function AnkiNote:get_custom_context(pre_s, pre_c, post_s, post_c)
 end
 
 function AnkiNote:get_picture_context()
-    if not self.ui.document then
-        return
-    end
     local meta = self.ui.document._anki_metadata
     if not meta then
         return
@@ -271,7 +265,7 @@ function AnkiNote:new(popup_dict)
         selected_dict = popup_dict.results[popup_dict.dict_index],
         -- indicates that popup_dict relates to word in book
         -- this can still be set to false later when the user looks up a word in a book, but then modifies the looked up word
-        contextual_lookup = self.ui.highlight and self.ui.highlight.selected_text ~= nil,
+        contextual_lookup = self.ui.highlight.selected_text ~= nil,
         word_trim = { before = "", after = "" },
         tags = { "KOReader" },
     }