Fix runnable branch callbacks (#11091)

We aren't calling on_chain_end here unless we use the default option

libs/langchain/langchain/schema/runnable/base.py

@@ -867,14 +867,15 @@ class RunnableBranch(Serializable, Runnable[Input, Output]):
                 )
 
                 if expression_value:
-                    return runnable.invoke(
+                    output = runnable.invoke(
                         input,
                         config=patch_config(
                             config,
                             callbacks=run_manager.get_child(tag=f"branch:{idx + 1}"),
                         ),
                     )
-
+                    break
+            else:
                 output = self.default.invoke(
                     input,
                     config=patch_config(
@@ -911,7 +912,7 @@ class RunnableBranch(Serializable, Runnable[Input, Output]):
                 )
 
                 if expression_value:
-                    return await runnable.ainvoke(
+                    output = await runnable.ainvoke(
                         input,
                         config=patch_config(
                             config,
@@ -919,7 +920,8 @@ class RunnableBranch(Serializable, Runnable[Input, Output]):
                         ),
                         **kwargs,
                     )
-
+                    break
+            else:
                 output = await self.default.ainvoke(
                     input,
                     config=patch_config(