Error: Opening Robot Framework log failed
The easiest thing to do is (if there are no worries on security aspects) also a permanent fix.

open the jenkins.xml file and 
add the following
<arguments>-Xrs -Xmx256m -Dhudson.lifecycle=hudson.lifecycle.WindowsServiceLifecycle -Dhudson.model.DirectoryBrowserSupport.CSP=""  -jar "%BASE%\jenkins.war" --  httpPort=8080 --webroot="%BASE%\war"</arguments>
restart the jenkins server
rerun your jenkins jobs to see the result files.

If we are using the script console, every time you restart the jenkins server, the changes will be lost.
If I open any .html file that generated by Robot Framework and try to convert it in any other format(for example, docx formate) using either any python code or inbuilt command line tool that are available. I am getting below error,

Opening Robot Framework log failed

•          Verify that you have JavaScript enabled in your browser.
•          Make sure you are using a modern enough browser. Firefox 3.5, IE 8, or equivalent is required, newer browsers are recommended.
•          Check are there messages in your browser's JavaScript error log. Please report the problem if you suspect you have encountered a bug.
·      I am getting this error even though I have already enabled JavaScript in my browser.I am using Mozilla Firefox version 45.0.2 on mac. 
Can anyone please help me to solve this issue?