Fix static path matching issue in macaron (#40023)

Co-authored-by: Malcolm Holmes <mdh@odoko.co.uk>

pkg/api/dashboard_snapshot.go

@@ -147,6 +147,10 @@ func CreateDashboardSnapshot(c *models.ReqContext, cmd models.CreateDashboardSna
 // GET /api/snapshots/:key
 func GetDashboardSnapshot(c *models.ReqContext) response.Response {
 	key := macaron.Params(c.Req)[":key"]
+	if len(key) == 0 {
+		return response.Error(404, "Snapshot not found", nil)
+	}
+
 	query := &models.GetDashboardSnapshotQuery{Key: key}
 
 	err := bus.Dispatch(query)
@@ -211,6 +215,9 @@ func deleteExternalDashboardSnapshot(externalUrl string) error {
 // GET /api/snapshots-delete/:deleteKey
 func DeleteDashboardSnapshotByDeleteKey(c *models.ReqContext) response.Response {
 	key := macaron.Params(c.Req)[":deleteKey"]
+	if len(key) == 0 {
+		return response.Error(404, "Snapshot not found", nil)
+	}
 
 	query := &models.GetDashboardSnapshotQuery{DeleteKey: key}
 
@@ -241,6 +248,9 @@ func DeleteDashboardSnapshotByDeleteKey(c *models.ReqContext) response.Response
 // DELETE /api/snapshots/:key
 func DeleteDashboardSnapshot(c *models.ReqContext) response.Response {
 	key := macaron.Params(c.Req)[":key"]
+	if len(key) == 0 {
+		return response.Error(404, "Snapshot not found", nil)
+	}
 
 	query := &models.GetDashboardSnapshotQuery{Key: key}