option should not be null when modifying column

src/common/backend/parser/gram.y

@@ -3424,7 +3424,7 @@ modify_column_cmd:
 					$$ = (Node *)n;
 				}
 			/* modify column comments start */
-			| COLUMN ColId opt_column_options
+			| COLUMN ColId column_options
 				{
 					AlterTableCmd *n = makeNode(AlterTableCmd);
 					ColumnDef *def = makeNode(ColumnDef);
@@ -3436,7 +3436,7 @@ modify_column_cmd:
 					$$ = (Node *)n;
 				}
 			;
-			| ColId opt_column_options
+			| ColId column_options
 				{
 					AlterTableCmd *n = makeNode(AlterTableCmd);
 					ColumnDef *def = makeNode(ColumnDef);

src/test/regress/expected/b_comments.out

@@ -55,6 +55,16 @@ create database b_comments dbcompatibility 'B';
 \c b_comments
 create schema b_comments;
 set search_path to 'b_comments';
+/* unsupported */
+create table test_unsupported(id int);
+alter table test_unsupported modify column id;
+ERROR:  syntax error at or near ";"
+LINE 1: alter table test_unsupported modify column id;
+                                                     ^
+alter table test_unsupported modify id;
+ERROR:  syntax error at or near ";"
+LINE 1: alter table test_unsupported modify id;
+                                              ^
 /* sanity check */
 create table test_row(a int not null comment 'test_row.a', b int not null comment 'test_row.b') comment 'test_row';
 create index on test_row(a,b) comment 'test_row_index';
@@ -236,8 +246,9 @@ where pc.relname = 'uq_0034';
 (1 row)
 
 drop schema b_comments cascade;
-NOTICE:  drop cascades to 15 other objects
-DETAIL:  drop cascades to table test_row
+NOTICE:  drop cascades to 16 other objects
+DETAIL:  drop cascades to table test_unsupported
+drop cascades to table test_row
 drop cascades to table test_column
 drop cascades to table test
 drop cascades to table partition_test

src/test/regress/sql/b_comments.sql

@@ -38,6 +38,11 @@ create database b_comments dbcompatibility 'B';
 \c b_comments
 create schema b_comments;
 set search_path to 'b_comments';
+/* unsupported */
+create table test_unsupported(id int);
+alter table test_unsupported modify column id;
+alter table test_unsupported modify id;
+
 /* sanity check */
 create table test_row(a int not null comment 'test_row.a', b int not null comment 'test_row.b') comment 'test_row';
 create index on test_row(a,b) comment 'test_row_index';