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 this link [https://gis.stackexchange.com/questions/108655/raster-to-polygon-conversion] 
so it needs some changes because of "unsigned integer" and ...that i dont know .  how can i correct this code ?  I 'm getting an error while executing it. Could you have some suggestion please?

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)