merged drives disappear

I'm receiving errors when trying to merge any drives:

"Fatal error: Call to a member function fetch_assoc() on boolean in /home/tesla/public_html/driveCalc.php on line 614"

Rather than potentially losing my trip again, is it safe to add the third leg of the trip into the merge, or is this still not a function of merge?

You still can't merge three drives together.  Only two drives can be merged together.

Hi, I just did a trip from Tauranga to Auckland but stopped for a coffee and a toilet break. I did a merge of the first part of the trip, then tried to do a merge for the second part and all of a sudden one of my trips has disappeared, i tried to un merge but still missing one of my trips. Please can you take a look

Thanks.  I believe I restored the drive and corrected the merge page to not show the merge button when there's no available drive to merge with.

I merged a drive 2 with another drive 3 this morning.  Then I tried to merge the second leg of my morning commute 4.  The last drive disappeared.

Sorry for the delay.  Somehow I wasn't notified of your reply.  Drive 4 should now show up again.

Thank you.  The merging drives wasn't designed to merge a drive with another merged drive and then unmerging them.  I have put in a catch to prevent the merging of a drive with another merged drive.