Avoiding a call of copy_file() with a null pointer.

git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@5352 35c25a1d-7b9e-4130-9fde-d3aeb78583b8

ChangeLog

+2015-08-11  Benno Schulenberg  <bensberg@justemail.net>
+	* src/files.c (write_file): Avoid calling copy_file() with a null
+	pointer.  Found with cppcheck.
+
 2015-08-09  Benno Schulenberg  <bensberg@justemail.net>
 	* src/global.c, src/help.c (help_init), src/nano.c (do_toggle, main),
 	src/winio.c (display_string, statusbar): Allow toggling the display

src/files.c

@@ -2007,7 +2007,7 @@ bool write_file(const char *name, FILE *f_open, bool tmp, append_type
 	    }
 	}
 
-	if (copy_file(f_source, f) != 0) {
+	if (f_source == NULL || copy_file(f_source, f) != 0) {
 	    statusbar(_("Error writing %s: %s"), tempname,
 		strerror(errno));
 	    unlink(tempname);