ci: dont crash if testing matrix is empty

Author: Borda

.actions/git-diff-sync.sh

@@ -30,4 +30,3 @@ git merge --ff -s resolve origin/$1
 python _TEMP/.actions/assistant.py group-folders target-diff.txt --fpath_actual_dirs "['dirs-$b1.txt', 'dirs-$b2.txt']"
 printf "\n================\nChanged folders:\n----------------\n" && cat changed-folders.txt
 printf "\n================\nDropped folders:\n----------------\n" && cat dropped-folders.txt
-

.actions/requires.txt

@@ -1,6 +1,6 @@
 Fire
 tqdm
-PyYAML
+PyYAML <6.0.0  # todo: racing issue with cython compile
 wcmatch
 requests
 pip

.azure/ipynb-validate.yml

@@ -37,6 +37,7 @@ jobs:
         name: mtrx
         displayName: "Changed matrix"
       - bash: echo '$(mtrx.dirs)' | python -m json.tool
+        continueOnError: "true" # not crash if the matrix is empty
         displayName: "Show matrix"
 
   - job: ipython