fix: add safe dictionary access for bedrock credentials (#11860)

api/core/model_runtime/model_providers/bedrock/get_bedrock_client.py

+from collections.abc import Mapping
+
 import boto3
 from botocore.config import Config
 
+from core.model_runtime.errors.invoke import InvokeBadRequestError
+
+
+def get_bedrock_client(service_name: str, credentials: Mapping[str, str]):
+    region_name = credentials.get("aws_region")
+    if not region_name:
+        raise InvokeBadRequestError("aws_region is required")
+    client_config = Config(region_name=region_name)
+    aws_access_key_id = credentials.get("aws_access_key_id")
+    aws_secret_access_key = credentials.get("aws_secret_access_key")
 
-def get_bedrock_client(service_name, credentials=None):
-    client_config = Config(region_name=credentials["aws_region"])
-    aws_access_key_id = credentials["aws_access_key_id"]
-    aws_secret_access_key = credentials["aws_secret_access_key"]
     if aws_access_key_id and aws_secret_access_key:
         # use aksk to call bedrock
         client = boto3.client(

api/core/model_runtime/model_providers/bedrock/rerank/rerank.py

                 }
             )
         modelId = model
-        region = credentials["aws_region"]
+        region = credentials.get("aws_region")
+        # region is a required field
+        if not region:
+            raise InvokeBadRequestError("aws_region is required in credentials")
         model_package_arn = f"arn:aws:bedrock:{region}::foundation-model/{modelId}"
         rerankingConfiguration = {
             "type": "BEDROCK_RERANKING_MODEL",