small NPE fixed when accessing data from excel

appointment-import/src/main/java/smash/appointment/parse/XlsxCalendarProcessor.java

@@ -62,7 +62,7 @@ public class XlsxCalendarProcessor {
 
 		CellParser parser = new CellParser();
 		parser.setSubjectDao(subjectDao);
-		
+
 		for (int weekOffset : weekStartRows) {
 			Row weekRow = sheet.getRow(weekOffset + dayOfMonthRowOffset);
 			for (int dayColumnOffset : dayColumns) {
@@ -89,13 +89,16 @@ public class XlsxCalendarProcessor {
 							}
 						}
 
-						String query = hourRow.getCell(dayColumnOffset).getStringCellValue();
+						Cell queryCell = hourRow.getCell(dayColumnOffset);
+						if (queryCell != null) {
+							String query = queryCell.getStringCellValue();
+
+							if (query != null && !query.isEmpty()) {
+								AppointmentEntry entry = parser.parseAppointment(query, hour);
+								entry.setDay(day);
 
-						if (query != null && !query.isEmpty()) {
-							AppointmentEntry entry = parser.parseAppointment(query, hour);
-							entry.setDay(day);
-							
-							result.add(entry);
+								result.add(entry);
+							}
 						}
 					}
 				}