fix: is_protocol() not returning a boolean (#180)

Returning a string instead of a boolean is fine in most cases,
but if the result gets compared against a boolean this breaks things.

scripts/uosc.lua

@@ -778,7 +778,7 @@ end
 -- Check if path is a protocol, such as `http://...`
 ---@param path string
 function is_protocol(path)
-	return type(path) == 'string' and path:match('^%a[%a%d-_]+://')
+	return type(path) == 'string' and path:match('^%a[%a%d-_]+://') ~= nil
 end
 
 ---@param path string