fix gdb stub causing the emulator to hang on undefined instructions (#2054)

* dont hang on undefined instruction

* Add spaces

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Co-authored-by: Kemal Afzal <RSDuck@users.noreply.github.com>

src/debug/GdbStub.h

@@ -152,6 +152,7 @@ public:
 	int RespFmt(const char* fmt, ...);
 
 	int RespStr(const char* str);
+	inline bool IsConnected() { return ConnFd > 0; }
 
 private:
 	void Disconnect();