Fix region cache update error when handle not leader

Signed-off-by: yongman <yming0221@gmail.com>

Author: yongman

src/region_cache.rs

@@ -209,9 +209,11 @@ impl<C: RetryClientTrait> RegionCache<C> {
         let mut cache = self.region_cache.write().await;
         let region_entry = cache
             .ver_id_to_region
-            .get_mut(&ver_id)
-            .ok_or(Error::EntryNotFoundInRegionCache)?;
-        region_entry.leader = Some(leader);
+            .get_mut(&ver_id);
+        if let Some(region) = region_entry {
+            region.leader = Some(leader);
+        }
+
         Ok(())
     }