Gracefully handle missing xref object

Do not raise if no object exists at xref for method "Document.xref_object(xref)".

Author: JorjMcKie

src/__init__.py

@@ -6105,17 +6105,18 @@ def xref_object(self, xref, compressed=0, ascii=0):
         """Get xref object source as a string."""
         if self.is_closed:
             raise ValueError("document closed")
-        if g_use_extra:
-            ret = extra.xref_object( self.this, xref, compressed, ascii)
-            return ret
         pdf = _as_pdf_document(self)
         xreflen = mupdf.pdf_xref_len(pdf)
         if not _INRANGE(xref, 1, xreflen-1) and xref != -1:
             raise ValueError( MSG_BAD_XREF)
-        if xref > 0:
-            obj = mupdf.pdf_load_object(pdf, xref)
-        else:
-            obj = mupdf.pdf_trailer(pdf)
+        try:
+            if xref > 0:
+                obj = mupdf.pdf_load_object(pdf, xref)
+            else:
+                obj = mupdf.pdf_trailer(pdf)
+        except Exception:
+            message(f"No object at {xref=}")
+            return "null"
         res = JM_object_to_buffer(mupdf.pdf_resolve_indirect(obj), compressed, ascii)
         text = JM_EscapeStrFromBuffer(res)
         return text
@@ -6166,7 +6167,7 @@ def xref_stream(self, xref):
         xreflen = mupdf.pdf_xref_len( pdf)
         if not _INRANGE(xref, 1, xreflen-1) and xref != -1:
             raise ValueError( MSG_BAD_XREF)
-        if xref >= 0:
+        if xref > 0:
             obj = mupdf.pdf_new_indirect( pdf, xref, 0)
         else:
             obj = mupdf.pdf_trailer( pdf)
@@ -6184,7 +6185,7 @@ def xref_stream_raw(self, xref):
         xreflen = mupdf.pdf_xref_len( pdf)
         if not _INRANGE(xref, 1, xreflen-1) and xref != -1:
             raise ValueError( MSG_BAD_XREF)
-        if xref >= 0:
+        if xref > 0:
             obj = mupdf.pdf_new_indirect( pdf, xref, 0)
         else:
             obj = mupdf.pdf_trailer( pdf)