Fix bug where one missing index.json caused no ensembles to be loaded

This is not without pitfalls, as the missing ensemble could be related to
an ensemble that still exists.

src/ert/storage/local_storage.py

@@ -118,22 +118,21 @@ def _load_index(self) -> _Index:
 
     @no_type_check
     def _load_ensembles(self):
-        try:
-            ensembles = []
-            for ensemble_path in (self.path / "ensembles").iterdir():
+        if not (self.path / "ensembles").exists():
+            return {}
+        ensembles = []
+        for ensemble_path in (self.path / "ensembles").iterdir():
+            try:
                 ensemble = self._load_ensemble(ensemble_path)
                 ensembles.append(ensemble)
-
-            # Make sure that the ensembles are sorted by name in reverse. Given
-            # multiple ensembles with a common name, iterating over the ensemble
-            # dictionary will yield the newest ensemble first.
-            ensembles = sorted(ensembles, key=lambda x: x.started_at, reverse=True)
-            return {
-                x.id: x
-                for x in sorted(ensembles, key=lambda x: x.started_at, reverse=True)
-            }
-        except FileNotFoundError:
-            return {}
+            except FileNotFoundError:
+                continue
+        # Make sure that the ensembles are sorted by name in reverse. Given
+        # multiple ensembles with a common name, iterating over the ensemble
+        # dictionary will yield the newest ensemble first.
+        return {
+            x.id: x for x in sorted(ensembles, key=lambda x: x.started_at, reverse=True)
+        }
 
     def _load_ensemble(self, path: Path) -> Any:
         return LocalEnsembleReader(self, path)