autogenerate a minimal NULL value sequence for unknown pointer types This

* gentest.py testapi.c: autogenerate a minimal NULL value sequence
  for unknown pointer types
* HTMLparser.c SAX2.c chvalid.c encoding.c entities.c parser.c
  parserInternals.c relaxng.c valid.c xmlIO.c xmlreader.c
  xmlsave.c xmlschemas.c xmlschemastypes.c xmlstring.c xpath.c
  xpointer.c: This uncovered an impressive amount of entry points
  not checking for NULL pointers when they ought to, closing all
  the open gaps.
Daniel
diff --git a/relaxng.c b/relaxng.c
index 146e9ea..8bd4d23 100644
--- a/relaxng.c
+++ b/relaxng.c
@@ -7671,6 +7671,8 @@
 void
 xmlRelaxNGDump(FILE * output, xmlRelaxNGPtr schema)
 {
+    if (output == NULL)
+        return;
     if (schema == NULL) {
         fprintf(output, "RelaxNG empty or failed to compile\n");
         return;
@@ -7700,6 +7702,8 @@
 void
 xmlRelaxNGDumpTree(FILE * output, xmlRelaxNGPtr schema)
 {
+    if (output == NULL)
+        return;
     if (schema == NULL) {
         fprintf(output, "RelaxNG empty or failed to compile\n");
         return;