Holding backspace to undo changes in bug search on new update form removes previously entered bugs

[bowlofeggs]

Today I was working on adding an update with about 20 packages in it, and I was searching for quite a few bugs. I decided to hold backspace to remove what I had typed into the search form, and instead of simply going back to the beginning of the field and stopping, it removed all the bugs I had selected up to that point. This was frustrating since I had spent a lot of time finding those bugs.