add fallback source

Actions/check_mcv.py

@@ -41,6 +41,7 @@ def update_library(version_mainfest, version_libloc:str, ver_type:str, ver_id:st
     #gen content
     content = '---\n'
     content += 'version-image-link: null\n'
+    content += 'version-image-link-fallback: null\n'
     content += 'not_finished: true\n'
     content += f'server-jar: {get_server_jar(version_mainfest, ver_id)}\n'
     content += 'translator: null\n'

Project/libraries/Versions/Release/1.21.7.md

@@ -1,5 +1,6 @@
 ---
 version-image-link: https://i0.hdslb.com/bfs/archive/19df87864d1c7fabfddad81382aef48bdb579436.png
+version-image-link-fallback: https://i0.hdslb.com/bfs/archive/19df87864d1c7fabfddad81382aef48bdb579436.png
 server-jar: https://piston-data.mojang.com/v1/objects/05e4b48fbc01f0385adb74bcff9751d34552486c/server.jar
 translator: 最亮的信标
 cats: ['1.21','1.21.6']

Project/structures/components/VersionHeaderImage.xaml

@@ -1,5 +1,5 @@
 <Border Style="{StaticResource VersionImageBorder}">
-<local:MyImage Source="${version-image-link}" Style="{StaticResource VersionImage}"/>
+<local:MyImage Source="${version-image-link}" ${@IF|${version-image-link-fallback}|FallbackSource="${version-image-link-fallback}" } Style="{StaticResource VersionImage}"/>
 </Border>
 <Border Style="{StaticResource VersionTitleBorder}">
 <TextBlock Style="{StaticResource VersionTitleBlock}" Text="${version-id}" />