`ext_flg` incorrect, `isExtendedFrame( )` is incorrect !!

[dreamer1048576]

As title,
No one/progress will clean the ext_flg, so the function isExtendedFrame( ) is INCORRECT !
After you send a ext frame, all isExtendedFrame() will return ALWAYS =1 , even you had receive a classic Standard Frame data .
And no one can call clearMsg( ) .

    uint8_t ext ;
// ... ...
              ext = CAN.isExtendedFrame();
              Serial.print("CAN.isExtendedFrame:=");   Serial.println(ext);

---

... After sending a ext frame :

CAN.isExtendedFrame:=1
ID=000007ff,8,0011223344556677
CAN.isExtendedFrame:=1
ID=000007ff,8,0011223344556677

Actually, the id=0x7ff is a Standard Frame !

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Copy From : DFRobot/DFRobot_MCP2515#1