The bug
Game crashes when resource pack selected.
How to reproduce
Start Minecraft 1.12.x and load a resource pack
Close Minecraft and start latest snapshot with resource pack still selected
→ Game crashes while launching
Crash report
17w47b\: [^crash-2017-11-25_10.58.20-client.txt]
Description: Initializing game
java.lang.IllegalArgumentException: Non [a-z0-9/._-] character in path of location: minecraft:blocks/stone frame
at mp.<init>(SourceFile:31)
at mp.<init>(SourceFile:36)
at cju.a(SourceFile:688)
at cju.k(SourceFile:562)
at cju.n(SourceFile:699)
at cju.a(SourceFile:188)
at cjv.a(SourceFile:23)
at sc.a(SourceFile:126)
at bmh.an(SourceFile:490)
at bmh.a(SourceFile:361)
at net.minecraft.client.main.Main.main(SourceFile:134)
Related issues
is duplicated by
relates to
Attachments
Comments

The resource pack is probably not ready for Minecraft 1.13 yet. The resource pack format has changed, even though the resource pack version number has not been increased yet.
Thank you for your report!
However, this issue has been temporarily closed as Awaiting Response.
We do not have enough information to find the cause of this issue.
Please attach the crash report found in [.minecraft|http://hopper.minecraft.net/help/guides/finding-minecraft-data-folder]/crash-reports/crash-<DATE>-client.txt
here.
Click here to find out where your .minecraft
folder is.
If you don't have a current crash report, please attach the launcher log which is located at [.minecraft|http://hopper.minecraft.net/help/guides/finding-minecraft-data-folder]/launcher_log.txt
.
Once you have attached the crash report or the launcher log, the report will be reopened automatically.
Quick Links:
📓 Issue Guidelines – 💬 Community Support – 📧 Customer Support – 📖 Game Wiki

A resource pack file name contains an invalid character. That makes sense! Is it possible to make mc 1.13 unload invalid resourcepacks while/before launching?
Your resource pack contains a location named minecraft:blocks/stone frame
, which is not a valid resource location anymore. In the meantime, use something like minecraft:blocks/stone_frame
or minecraft:blocks/stone-frame
instead.
Thank you for your report!
However, this issue is a Duplicate of MC-122206.
It has been linked to this report. If you have additional information, please add it to that report.
Please search before reporting, as it's likely that one exists already.
Quick Links:
📓 Issue Guidelines – 💬 Community Support – 📧 Customer Support – 📖 Game Wiki
Is it possible to make mc 1.13 unload invalid resourcepacks while/before launching?
Minecraft will not load old resource packs once the resourcepack version number is increased, which it is not yet.
Anyway, it shouldn't crash if the resource pack is invalid. It should just not load the pack. As I said, tracked at MC-122206.
Changed my mind and reopened, the other issue is about data packs, not resource packs, and doesn't cause a crash.
Spaces are not supported in filenames.

Is this still an issue in the latest 1.13-prereleases?
Does it still crash or only warn in the logfile?
If still crashing, please attach an "affected" resource pack.

It doen't crash anymore.
log: "Removed resource pack Adventure x16 from options because it is no longer compatible"

Thanks for the feedback.