Log and Continue on OSError while collating dates for date filters

Log to understand if error, date can be handled better
Mitigates #172

src/khoj/search_filter/date_filter.py

@@ -41,6 +41,9 @@ class DateFilter(BaseFilter):
                         date_in_entry = datetime.strptime(date_in_entry_string, "%Y-%m-%d").timestamp()
                     except ValueError:
                         continue
+                    except OSError:
+                        logger.debug(f"OSError: Ignoring unprocessable date in entry: {date_in_entry_string}")
+                        continue
                     self.date_to_entry_ids[date_in_entry].add(id)
 
     def can_filter(self, raw_query):