fix Droid Sans Fallback not registered to crengine

frontend/document/credocument.lua

@@ -22,7 +22,7 @@ local CreDocument = Document:new{
     line_space_percent = 100,
     default_font = G_reader_settings:readSetting("cre_font") or "Noto Serif",
     header_font = G_reader_settings:readSetting("header_font") or "Noto Sans",
-    fallback_font = G_reader_settings:readSetting("fallback_font") or "Droid Sans Fallback",
+    fallback_font = G_reader_settings:readSetting("fallback_font") or "Droid Sans Fallback H",
     default_css = "./data/cr3.css",
     options = CreOptions,
 }

frontend/ui/font.lua

@@ -83,7 +83,8 @@ function Font:_readList(target, dir, effective_dir)
             self:_readList(target, dir.."/"..f, effective_dir..f.."/")
         else
             local file_type = string.lower(string.match(f, ".+%.([^.]+)") or "")
-            if file_type == "ttf" or file_type == "cff" or file_type == "otf" then
+            if file_type == "ttf" or file_type == "ttc"
+                or file_type == "cff" or file_type == "otf" then
                 table.insert(target, effective_dir..f)
             end
         end