Fix multipartitions run length encoding error (#12329)

Seen here:
https://app.datadoghq.com/apm/trace/3303427780901995569?spanID=13139862780265732778&spanViewType=errors

This PR is mostly just snapshot updates and is hopefully fairly fast to
review!

The root cause is that the first dimension has no partitions. This can
happen on an empty static partitions definition, or a time window
partitions definition where the start time is in the future.

This PR adds a check for this case, exiting early if the primary
dimension has no partition keys. The run length encoding will still
succeed if the secondary dimension has no partition keys.

python_modules/dagster-graphql/dagster_graphql/implementation/fetch_assets.py

@@ -456,12 +456,17 @@ def get_2d_run_length_encoded_materialized_partitions(
     unevaluated_idx = 0
     range_start_idx = 0  # pointer to first dim1 partition with same dim2 materialization status
 
+    if len(dim1_keys) == 0 or len(secondary_dim.partitions_def.get_partition_keys()) == 0:
+        return GrapheneMultiPartitions(ranges=[], primaryDimensionName=primary_dim.name)
+
     while unevaluated_idx <= len(dim1_keys):
         if (
             unevaluated_idx == len(dim1_keys)
             or dim2_partition_subset_by_dim1[dim1_keys[unevaluated_idx]]
             != dim2_partition_subset_by_dim1[dim1_keys[range_start_idx]]
         ):
+            # Add new multipartition range if we've reached the end of the dim1 keys or if the
+            # second dimension subset is different than the previous dim1 key
             if len(dim2_partition_subset_by_dim1[dim1_keys[range_start_idx]]) > 0:
                 # Do not add to materialized_2d_ranges if the dim2 partition subset is empty
                 start_key = dim1_keys[range_start_idx]

python_modules/dagster-graphql/dagster_graphql_tests/graphql/repo.py

@@ -1857,6 +1857,19 @@ def multipartitions_2(multipartitions_1):
     return multipartitions_1
 
 
+no_partitions_multipartitions_def = MultiPartitionsDefinition(
+    {
+        "a": StaticPartitionsDefinition([]),
+        "b": StaticPartitionsDefinition([]),
+    }
+)
+
+
+@asset(partitions_def=no_partitions_multipartitions_def)
+def no_multipartitions_1():
+    return 1
+
+
 # For now the only way to add assets to repositories is via AssetGroup
 # When AssetGroup is removed, these assets should be added directly to repository_with_named_groups
 named_groups_job = AssetGroup(
@@ -1956,6 +1969,12 @@ def define_asset_jobs():
             AssetSelection.assets(multipartitions_1, multipartitions_2),
             partitions_def=multipartitions_def,
         ),
+        no_multipartitions_1,
+        define_asset_job(
+            "no_multipartitions_job",
+            AssetSelection.assets(no_multipartitions_1),
+            partitions_def=no_partitions_multipartitions_def,
+        ),
         SourceAsset("diamond_source"),
         fresh_diamond_top,
         fresh_diamond_left,