Ignore empty line in autogen.input

Change-Id: I5a640c996779ba548c1b4772820eaa799537c1af
Reviewed-on: https://gerrit.libreoffice.org/4991Reviewed-by: Luboš Luňák <l.lunak@suse.cz>
Tested-by: Luboš Luňák <l.lunak@suse.cz>

autogen.sh

@@ -76,6 +76,8 @@ sub read_args($)
             }
         } elsif ( substr($_, 0, 1) eq "#" ) {
             # comment
+        } elsif ( length == 0 ) {
+            # empty line
         } else {
             push @lst, $_;
         }