fix regression caused by 'TextBuilder.advanceSearchPos' function. We were previously checking if the absIdx is in the search range and advancing based on whether that is true or false, but we should only advance if absIdx is after the search range

fcore/text-builder.sml

@@ -333,14 +333,10 @@ struct
     end
 
   fun advanceSearchPos (absIdx, searchPos, searchHd, searchLen) =
-    let
-      val searchIdx = Vector.sub (searchHd, searchPos)
-    in
-      if absIdx >= searchIdx andalso absIdx < searchIdx + searchLen then
-        searchPos
-      else
-        searchPos + 1
-    end
+    if isAfterSearchRange (absIdx, searchPos, searchHd, searchLen) then
+      searchPos + 1
+    else
+      searchPos
 
   fun buildTextStringSearch
     ( pos