Fix a bug in the GeoJSON handling when there are no active polygons

internal/normalizers/spc/convective_outlook.go

@@ -87,6 +87,17 @@ func buildConvectiveOutlook(bundle spcprovider.RawConvectiveOutlookBundle, fallb
 		}
 
 		for i, feature := range collection.Features {
+			if spcprovider.IsEmptyGeometryCollection(feature.Geometry) {
+				issuedAt, err := parseRequiredSPCTime(feature.Properties.IssueISO, fmt.Sprintf("product %s feature %d.ISSUE_ISO", product.Key, i))
+				if err != nil {
+					return model.WeatherOutlookRun{}, time.Time{}, err
+				}
+				if latestIssue.IsZero() || issuedAt.After(latestIssue) {
+					latestIssue = issuedAt
+				}
+				continue
+			}
+
 			outlook, err := mapFeature(product, feature, i, point, discussion)
 			if err != nil {
 				return model.WeatherOutlookRun{}, time.Time{}, err