allow repeated PAUSE requests (#107)

internal/client/client.go

@@ -855,7 +855,9 @@ func (c *Client) handleRequest(req *base.Request) error {
 
 	case base.PAUSE:
 		err := c.checkState(map[state]struct{}{
+			statePrePlay:   {},
 			statePlay:      {},
+			statePreRecord: {},
 			stateRecord:    {},
 		})
 		if err != nil {
@@ -870,7 +872,11 @@ func (c *Client) handleRequest(req *base.Request) error {
 				"Session": base.HeaderValue{sessionId},
 			},
 		})
+
+		if c.state == statePlay || c.state == stateRecord {
 			return errStateInitial
+		}
+		return nil
 
 	case base.TEARDOWN:
 		// close connection silently