fix: update blank guard usage and fix issue

example/manifest/ppic.toml

@@ -77,6 +77,7 @@ default = '@C:\path\to\ppic.exe,-1001'
 
 # And more string resources...
 jpg = '@C:\path\to\ppic.exe,-1011'
+jfif = '@C:\path\to\ppic.exe,-1050'
 gif = '@C:\path\to\ppic.exe,-1012'
 bmp = '@C:\path\to\ppic.exe,-1013'
 png = '@C:\path\to\ppic.exe,-1014'