You could use something like this which does not produce errors when a file does not exist. On my machine, I get a four page document (files 1 and 4 exist; files 2 and 3 do not).
Note: \newpage, \pagebreak and \clearpage do nothing to an empty page, so you need to add something invisible first. BTW, \clearpage is used primarily to clear the float queue.
Best Answer
Writing
\newpage\phantom{blabla}
twice or more will do the job.