If cell doesn't contain text, populate nothing in another cell?

Column E = Message Text
Column I = Numeric Value (populated field from Column E)

Column E may contain a message like, "Processing steps".
Or, it could contain a message like, "Processing steps. Header:1, Lines: 123."

If column E contains the word "Lines: ", I need to populate Column I with the number after the word 'Lines: '.
There is also a period at the end of the string that I do not want to include.


Here is what I have so far...

=INT(MID(E4,FIND("Lines: ",E4)+7,LEN(E4)

This works great if the specified word is found, but produces a #Value! if not found.

My question is, if column E doesn't contain "Lines: (numeric value).", how can I populate Column I to output nothing?
I understand I need to create an IF statement, but not sure how.

Any suggestions?