fix: language M rule 4 not removing late UUs

Logic/Language/M.hs

@@ -40,7 +40,7 @@ mRule2 _ = []
 mRule3 :: StringM -> [StringM]
 mRule3 string@(M:xs) = (M:) <$> aux xs
   where
-    aux (I:xs@(I:I:xs')) = (U:xs'):((I:) <$> aux xs)
+    aux (x@I:xs@(I:I:xs')) = (U:xs'):((x:) <$> aux xs)
     aux (x:xs) = (x:) <$> aux xs
     aux _  = []
 mRule3 _ = []
@@ -49,7 +49,7 @@ mRule3 _ = []
 mRule4 :: StringM -> [StringM]
 mRule4 string@(M:xs) = (M:) <$> aux xs
   where
-    aux (U:U:xs) = [xs]
+    aux (x@U:xs@(U:xs')) = xs':((x:) <$> aux xs)
     aux (x:xs) = (x:) <$> aux xs
     aux _ = []
 mRule4 _ = []