BaseTools:change some incorrect parameter defaults

BZ:https://bugzilla.tianocore.org/show_bug.cgi?id=1858

for Dict={},There are pitfalls in the way this default parameter is set
and Dict is not used in functions, other functions have these two cases,
I will change some incorrect parameter defaults

This patch is going to fix this issue

Cc: Liming Gao <liming.gao@intel.com>
Cc: Bob Feng <bob.c.feng@intel.com>
Signed-off-by: Zhiju.Fan <zhijux.fan@intel.com>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>

BaseTools/Source/Python/GenFds/Section.py

@@ -92,7 +92,7 @@ class Section (SectionClassObject):
     #   @param  FfsInf      FfsInfStatement object that contains this section data
     #   @param  Dict        dictionary contains macro and its value
     #
-    def GenSection(self, OutputPath, GuidName, SecNum, keyStringList, FfsInf = None, Dict = {}):
+    def GenSection(self, OutputPath, GuidName, SecNum, keyStringList, FfsInf = None, Dict = None):
         pass
 
     ## GetFileList() method