fix chunk method "Table" losing content when the Excel file has multi… (#4123)

…ple sheets

### What problem does this PR solve?
discussed in https://github.com/infiniflow/ragflow/pull/4102
- In excel_parser.py, `total` means the total number of rows in Excel,
but it return in the first iterate, that lead to the wrong `to_page`
- In table.py, it when Excel file has multiple sheets, it will be
divided into multiple parts, every part size is 3000, `data` may be
empty, because it has recorded in the last iterate.
### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

deepdoc/parser/excel_parser.py

@@ -90,7 +90,7 @@ class RAGFlowExcelParser:
             for sheetname in wb.sheetnames:
                 ws = wb[sheetname]
                 total += len(list(ws.rows))
-                return total
+            return total
 
         if fnm.split(".")[-1].lower() in ["csv", "txt"]:
             encoding = find_codec(binary)

rag/app/table.py

@@ -66,6 +66,8 @@ class Excel(ExcelParser):
                     continue
                 data.append(row)
                 done += 1
+            if np.array(data).size == 0:
+                continue
             res.append(pd.DataFrame(np.array(data), columns=headers))
 
         callback(0.3, ("Extract records: {}~{}".format(from_page + 1, min(to_page, from_page + rn)) + (