fix assert

git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@2697 35c25a1d-7b9e-4130-9fde-d3aeb78583b8

src/nano.c

@@ -2643,7 +2643,7 @@ void justify_format(filestruct *paragraph, size_t skip)
     assert(paragraph != NULL);
     assert(paragraph->data != NULL);
     assert(skip < strlen(paragraph->data));
-    assert(!isblank(paragraph->data[skip]));
+    assert(!is_blank_mbchar(paragraph->data + skip));
 
     end = paragraph->data + skip;
     new_paragraph_data = charalloc(strlen(paragraph->data) + 1);