NullPointerException in "fieldMaps" when trying to create mappings for 17w46a

[Bixilon]

I am trying to backport yarn mappings to 17w46a. I am using 18w46a to to this. See FabricMC/yarn/issues/2302 for more details.

I merged the jars for both versions, exported the mappings in Matcher and created a .match file. I haven't checked all matches, but I don't really care about them (most of them are just data fixers). See my files attached (1. matches, 2. the generated ones for 17w46a)

Next I try to run stich, but it fails:

moritz@moritz-tp:~/Games/Minecraft/fabric/intermediary$ java -Dstitch.counter=counter.txt -jar /home/moritz/Games/Minecraft/fabric/stitch/build/libs/stitch-0.6.0+local-all.jar updateIntermediary /home/moritz/Games/Minecraft/fabric/yarn2/18w43b-merged.jar /home/moritz/Games/Minecraft/fabric/yarn2/17w46a-merged.jar /home/moritz/Games/Minecraft/fabric/intermediary/mappings/18w43b.tiny /home/moritz/Games/Minecraft/fabric/intermediary/mappings/17w46a.tiny /home/moritz/Games/Minecraft/fabric/intermediary/matches/18w43b-17w46a.match
Read 4273 (2797) classes.
Populated subclass entries.
Joining MethodEntries...
Joined 10666 MethodEntries (0 unique, 4273 classes).
Collecting additional information...
- Done. -
Read 3579 (2125) classes.
Populated subclass entries.
Joining MethodEntries...
Joined 9332 MethodEntries (0 unique, 3579 classes).
Collecting additional information...
- Done. -
Loading remapping files...
Generating new mappings...
Target file exists - loading...
java.lang.NullPointerException: Cannot read field "fieldMaps" because "x0" is null
        at net.fabricmc.stitch.commands.GenMap$Class.access$000(GenMap.java:26)
        at net.fabricmc.stitch.commands.GenMap.load(GenMap.java:59)
        at net.fabricmc.stitch.commands.GenState.generate(GenState.java:98)
        at net.fabricmc.stitch.commands.CommandUpdateIntermediary.run(CommandUpdateIntermediary.java:87)
        at net.fabricmc.stitch.Main.main(Main.java:72)

Am I doing something wrong or how to solve this issue?

Thanks (again)

Moritz

17w46a.zip