Pressing backspace twice in snippet prevents tab from working again

[cssherry]

When in snippet, and press backspace to remove the highlighted selection, then press backspace again to remove extra space, user can no longer tab to the next selection.

Eg: For
"CASE ${1:value} WHEN ${2:option1} THEN ${3:result1} END", when user delete ${2:..}, and the space in front of the selection, they can no longer tab to ${3:...}

[cssherry]

I'm looking into this, currently looking in lib/ace/snippets.js file