fixing few potential problems

lib/core/common.py

@@ -2767,7 +2767,7 @@ def isNoneValue(value):
     """
 
     if isinstance(value, basestring):
-        return value == "None"
+        return value in ("None", "")
     elif isinstance(value, (list, tuple)):
         if len(value) == 1:
             return isNoneValue(value[0])

plugins/dbms/mssqlserver/enumeration.py

@@ -135,6 +135,7 @@ class Enumeration(GenericEnumeration):
                     _ = (rootQuery.blind.query if query == rootQuery.blind.count else rootQuery.blind.query2 if query == rootQuery.blind.count2 else rootQuery.blind.query3).replace("%s", db) % index
 
                     table = inject.getValue(_, inband=False, error=False)
+                    if not isNoneValue(table):
                         kb.hintValue = table
                         table = safeSQLIdentificatorNaming(table, True)
                         tables.append(table)

plugins/generic/enumeration.py

@@ -1449,7 +1449,7 @@ class Enumeration:
                         value = inject.getValue(query, blind=False)
 
                     if column == colList[0]:
-                        if isNoneValue(value) or not value:
+                        if isNoneValue(value):
                             breakRetrieval = True
                             break
                         else: