object_store careful range slicing

Ranges requested beyond the length of the resource can no longer
cause panics in the `coalesce_ranges` function.

object_store/src/util.rs

@@ -124,7 +124,7 @@ where
 
             let start = range.start - fetch_range.start;
             let end = range.end - fetch_range.start;
-            fetch_bytes.slice(start..end)
+            fetch_bytes.slice(start..end.min(fetch_bytes.len()))
         })
         .collect())
 }