Bug 1869867 - Update experimentation test suite to support smoke tests that don't use the message feature (#4828)

app/src/androidTest/java/org/mozilla/fenix/experimentintegration/conftest.py

@@ -67,12 +67,15 @@ def gradlewbuild(gradlewbuild_log):
 @pytest.fixture(name="experiment_data")
 def fixture_experiment_data(experiment_url):
     data = requests.get(experiment_url).json()
-    for item in data["branches"][0]["features"][0]["value"]["messages"].values():
-        item["surface"] = "homescreen"
-        item["style"] = "URGENT"
-        for count, trigger in enumerate(item["trigger"]):
-            if "USER_EN_SPEAKER" not in trigger:
-                del item["trigger"][count]
+    branches = next(iter(data.get("branches")), None)
+    features = next(iter(branches.get("features")), None)
+    if features.get("messages"):
+        for item in features["value"]["messages"].values():
+            item["surface"] = "homescreen"
+            item["style"] = "URGENT"
+            for count, trigger in enumerate(item["trigger"]):
+                if "USER_EN_SPEAKER" not in trigger:
+                    del item["trigger"][count]
     return [data]