Fix empty error page on BrokenTubeException

src/invidious/exceptions.cr

@@ -1,8 +1,12 @@
 # Exception used to hold the name of the missing item
 # Should be used in all parsing functions
-class BrokenTubeException < InfoException
+class BrokenTubeException < Exception
   getter element : String
 
   def initialize(@element)
   end
+
+  def message
+    return "Missing JSON element \"#{@element}\""
+  end
 end