I'm trying to automate the conversion of raster to polygon and the raster files are in "TIF" format which is a "floating point". I copy the code below from https://gis.stackexchange.com/questions/108655 
so it needs some changes because of "unsigned integer" and ...that I don't know.  

How can I correct this code?  

I'm getting an error while executing it.

> Runtime error  Traceback (most recent call last):   File "<string>",
> line 18, in <module> TypeError: 'NoneType' object is not iterable
> 

Code

    import arcpy, os
    from arcpy import env
    from arcpy.sa import *

    #To overwrite output
    arcpy.env.overwriteOutput = True

    #Set environment settings
    env.workspace = "K:\1400-10-20"

    outws="K:\1400-10-20\m"

    #checkout ArcGIS spatial analyst extension license
    arcpy.CheckOutExtension("Spatial")

    inraster = arcpy.ListRasters("*", "TIF")

    for i in inraster:
        filename=os.path.splitext(i)[0]
        outPolygons= outws + str(filename) + '.shape'
        field = "VALUE"
        arcpy.RasterToPolygon_conversion(i, outPolygons, "NO_SIMPLIFY", field)