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

@@ -211,24 +211,32 @@ class PptxConverter(DocumentConverter):
         return self._html_converter.convert_string(html_table).markdown.strip() + "\n"
 
     def _convert_chart_to_markdown(self, chart):
-        md = "\n\n### Chart"
-        if chart.has_title:
-            md += f": {chart.chart_title.text_frame.text}"
-        md += "\n\n"
-        data = []
-        category_names = [c.label for c in chart.plots[0].categories]
-        series_names = [s.name for s in chart.series]
-        data.append(["Category"] + series_names)
+        try:
+            md = "\n\n### Chart"
+            if chart.has_title:
+                md += f": {chart.chart_title.text_frame.text}"
+            md += "\n\n"
+            data = []
+            category_names = [c.label for c in chart.plots[0].categories]
+            series_names = [s.name for s in chart.series]
+            data.append(["Category"] + series_names)
 
-        for idx, category in enumerate(category_names):
-            row = [category]
-            for series in chart.series:
-                row.append(series.values[idx])
-            data.append(row)
+            for idx, category in enumerate(category_names):
+                row = [category]
+                for series in chart.series:
+                    row.append(series.values[idx])
+                data.append(row)
 
-        markdown_table = []
-        for row in data:
-            markdown_table.append("| " + " | ".join(map(str, row)) + " |")
-        header = markdown_table[0]
-        separator = "|" + "|".join(["---"] * len(data[0])) + "|"
-        return md + "\n".join([header, separator] + markdown_table[1:])
+            markdown_table = []
+            for row in data:
+                markdown_table.append("| " + " | ".join(map(str, row)) + " |")
+            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"