Assistance Hiding Gif

[Bane]

Bear with me, as I sometimes don't make much sense.

I have created a custom field, settable by admin/mod only, and would like to have the Post and Member information show a .gif with the name of the field. I accomplised this by using

<img src="{ imagesfolder }/$post[field5].gif">

Now my problem is, if the field is blank, it shows a large red blank image x. Which I must say is quite counterproductive to my needs.

So what I need is a way to hide this if the field is blank. but I am not sure how to go about this. I'm guessing I need to edit the showthread.php and member.php files, but I'm not sure where or how. I tried a little tampering but was unsuccessful.