Draft: Fix LGTM 'test for equality' warning (#4969)

* Draft: Fix LGTM 'test for equality' warning

ref: https://lgtm.com/projects/g/FreeCAD/FreeCAD/alerts/?mode=tree&ruleFocus=7900090

* FEM: source comment typo fixes

src/Mod/Draft/draftutils/units.py

@@ -95,7 +95,7 @@ def display_external(internal_value,
     if dim == 'Length':
         q = App.Units.Quantity(internal_value, App.Units.Length)
         if not unit:
-            if decimals == None and showUnit:
+            if decimals is None and showUnit:
                 return q.UserString
 
             conversion = q.getUserPreferred()[1]