Antlr4: Nested if-then-else in input requires a statement to parse correctly - antlr

Question

I have simplified my grammar and am testing it in http://lab.antlr.org/. It works for
// if column not exists CURRENTSCHEMA.TABLE_EXISTS.NO_SUCH_COLUMN
// if column not exists CURRENTSCHEMA.TABLE_EXISTS.NO_SUCH_COLUMN
alter table TABLE_EXISTS add column (NO_SUCH_COLUMN decimal(5,4));
// end if
xyz; <-------- required! Why???
// end if
NOTE: there must be a NL char after the last // end if, else the parsing does not work at all. How to fix that is a separate question. When I add to the line comment a (NL | EOF) as termination sequence it complains about missing a NL.
but if I remove that xyz; (I call that a statement) then it does not. It looks as if each if-then-else must have at least one statement.
However I have defined a statement as either a text with semicolon or a line comment and a line comment with // if ... // end if is considered a directive.
With the xyz; the tree is the expected, a line comment of type directive with a statement which has another line comment with directive. Without the xyz is is a line comment with directive and within is a regular line comment and a statement.
statement :
trailing
| linecomment
| text* ';' (NL | WS)* ;
Can anybody spot my mistake? I have checked the ordering, the length of the tokens but obviously I am missing something essential or I am simply blind.
This is how it should look like, two nested directive nodes.
Complete grammar file:
grammar Sqlscripts;
options { caseInsensitive = true; }
LINE_COMMENT_START: '//' ;
WS: [ \t\r\f]+ ;
NL: '\r\n' | 'r' | '\n' ;
OBJECT: 'OBJECT' ;
COLUMN: 'COLUMN' ;
END: 'END' ;
IF: 'IF' ;
SEMI: ';' ;
NOT: 'NOT' ;
DOT: '.' ;
COMMA: ',' ;
EXISTS: 'EXISTS' ;
WORD: ([A-Z_0-9!#$%&+:<>=?*#{}]
| '\\'
| ']' | '[' | '-')+ ;
trailing:
WS* NL ;
identifier:
WORD DOT WORD (DOT WORD)* ;
directive:
WS* directivecondition
statement*
directiveend ;
directivecondition:
IF WS*
(OBJECT | COLUMN ) WS*
(NOT WS*)? EXISTS WS+
identifier trailing ;
directiveend:
LINE_COMMENT_START WS* END WS+
IF trailing ;
linecomment:
LINE_COMMENT_START
(directive | (~(NL)* NL)) ;
text:
WORD
| identifier
| OBJECT
| COLUMN
| paramclause
| NOT
| EXISTS
| trailing
| linecomment
| WS+
;
// A statement is either a command terminated
statement :
trailing
| linecomment
| text* ';' (NL | WS)* ;
paramclause:
'(' param_list ')' ;
param_list:
text+ (COMMA text*)* ;
script:
statement* (NL | WS)* EOF;