MDEV-15114: Fix memory leaks

When innobase_allocate_row_for_vcol() returns true (for failure),
it may already have invoked mem_heap_create(). However, some callers
would fail to invoke mem_heap_free().

storage/innobase/row/row0ins.cc

@@ -966,8 +966,8 @@ row_ins_foreign_fill_virtual(
 
 	if (innobase_allocate_row_for_vcol(thd, index, &v_heap,
                                            &mysql_table,
-                                           &record, &vcol_storage))
-        {
+                                           &record, &vcol_storage)) {
+		if (v_heap) mem_heap_free(v_heap);
 		*err = DB_OUT_OF_MEMORY;
 		goto func_exit;
 	}

storage/innobase/row/row0upd.cc

@@ -1162,6 +1162,7 @@ row_upd_build_difference_binary(
 				&v_heap, heap, NULL, thd, mysql_table, record,
 				NULL, NULL, NULL);
 			if (vfield == NULL) {
+				if (v_heap) mem_heap_free(v_heap);
 				*error = DB_COMPUTE_VALUE_FAILED;
 				return(NULL);
 			}