Number format read fix (#741)

* fix UT-generated file names to be ignored
* fix cell value load with invalid number format ID
* fix PR issues

1 files changed, 6 insertions, 1 deletions

diff --git a/cell.go b/cell.go
index 1edfd24..22adefd 100644
--- a/cell.go
+++ b/cell.go
@@ -762,10 +762,15 @@ func (f *File) formattedValue(s int, v string) string {
 		return v
 	}
 	styleSheet := f.stylesReader()
+
 	if s >= len(styleSheet.CellXfs.Xf) {
 		return v
 	}
-	numFmtID := *styleSheet.CellXfs.Xf[s].NumFmtID
+	var numFmtID int
+	if styleSheet.CellXfs.Xf[s].NumFmtID != nil {
+		numFmtID = *styleSheet.CellXfs.Xf[s].NumFmtID
+	}
+
 	ok := builtInNumFmtFunc[numFmtID]
 	if ok != nil {
 		return ok(v, builtInNumFmt[numFmtID])