[anjuta] am-project: Fix a bug in configure.ac parser

[Sebastien Granjoux <sgranjoux src gnome org>]

commit 004cd9df87dac21ade0e1a11b522f2aadce0428c
Author: SÃbastien Granjoux <seb sfo free fr>
Date:   Sat Nov 5 17:22:48 2011 +0100

    am-project: Fix a bug in configure.ac parser
    
    I have seen it only with the next patch.

 plugins/am-project/ac-parser.y |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/plugins/am-project/ac-parser.y b/plugins/am-project/ac-parser.y
index 4f0e791..49cd9a5 100644
--- a/plugins/am-project/ac-parser.y
+++ b/plugins/am-project/ac-parser.y
@@ -803,7 +803,9 @@ expression_body:
     ;
 
 optional_spaces:
-	/* empty */
+	/* empty */ {
+		$$ = NULL;
+	}
 	| spaces
 	;