Bug report title is self-explanatory. A collectible version of Mind Blast is a Shadow spell, and the version you can get from Dreamplanner Zephrys does not have a spell school.
This does not seem to be intended considering that other spells that Zephrys can offer do have their spell schools applied correctly (if applicable). There are cards that matter about a spell having a Shadow spell school.
It appears to me that the version of Mind Blast the new Zephrys uses comes from Classic format (card id: VAN_DS1_233). The card watermark (indicating the set) seems to confirm this (check for example https://hearthstone.blizzard.com/en-us/cards/110796-dreamplanner-zephrys , related cards section).
Steps to reproduce and confirm a bug: play Dreamplanner Zephrys for cards that can potentially damage the enemy hero, and have him get Mind Blast. Then, to confirm it’s not just a visual glitch, play Defias Leper with no other Shadow spells in hand and see if his battlecry activates. (or a similar interaction with specifically Shadow spells)