Merge branch 'mysql-5.7-cluster-7.6' into mysql-8.0

Change-Id: I81efeda0204b35330d161baab7a5be4bd58f68f9

Author: frazerclement

storage/ndb/plugin/ha_ndbcluster.cc

@@ -13838,16 +13838,13 @@ int ha_ndbcluster::multi_range_start_retrievals(uint starting_range) {
         type_loc = enum_empty_unique_range;
       else {
         /*
-          This shouldn't really happen.
-
-          There aren't really any other errors that could happen on the read
-          without also aborting the transaction and causing execute() to
-          return failure.
-
-          (But we can still safely return an error code in non-debug builds).
+          Some operation error that did not cause transaction
+          rollback, but was unexpected when performing these
+          lookups.
+          Return error to caller, expecting caller to rollback
+          transaction.
         */
-        assert(false);
-        ERR_RETURN(error); /* purecov: deadcode */
+        ERR_RETURN(error);
       }
     }
   }