val in self.channels.items() can be float

Hi fellow,

thanks a looot for your library. Real nice work.

I ran into an issue (can't tell you the origin), but by using a constant stream following line in _Controller.py might create a float, which later on will crash the program:

# Get all channels values
               for key, val in self.channels.items():
                    # If channel in frame
                    if key - first < len(self.__frame):
                       self.__frame[key - first] = int(val[0])`

i placed an int() around the val[0]. Not sure if that's in general a good idea.

but it fixed the issue, that otherwise at this call would break the runtime.

def _transmit(self, frame: List[int], first: int):
        # Convert to a bytearray and pad the start of the frame
        # We're transmitting direct DMX data here, so a frame must start at channel 1, but can end early
        try:
            data = bytearray(([0] * (first - 1)) + frame)
            # The first byte in the type, and is `0` for normal DMX data
            data.insert(0, 0)

            # Write
            self.__device.send_break(100e-6)
            sleep(10e-6)
            self.__device.write(data)
        except:
            print("bad request")`
```

as you see I made a try / except for myself.

从 _Controller.py 中的通道值循环开始，检查 self.channels.items() 中的值如何传递到 _transmit。重现会产生 float 的恒定流情况，然后验证所选处理方式能够保留有效的 DMX 帧数据，并防止转换为 bytearray 时失败。