Handle not supported plot type in pptx (#1122)

* Handle not supported plot type in pptx
* Fixed formatting.

packages/markitdown/src/markitdown/converters/_pptx_converter.py

@@ -211,6 +211,7 @@ class PptxConverter(DocumentConverter):
         return self._html_converter.convert_string(html_table).markdown.strip() + "\n"
 
     def _convert_chart_to_markdown(self, chart):
+        try:
             md = "\n\n### Chart"
             if chart.has_title:
                 md += f": {chart.chart_title.text_frame.text}"
@@ -232,3 +233,10 @@ class PptxConverter(DocumentConverter):
             header = markdown_table[0]
             separator = "|" + "|".join(["---"] * len(data[0])) + "|"
             return md + "\n".join([header, separator] + markdown_table[1:])
+        except ValueError as e:
+            # Handle the specific error for unsupported chart types
+            if "unsupported plot type" in str(e):
+                return "\n\n[unsupported chart]\n\n"
+        except Exception:
+            # Catch any other exceptions that might occur
+            return "\n\n[unsupported chart]\n\n"