Fix crash on importing Java code attached to bug 368453:

The example uses the global scope and JavaImport crashes on adding
objects in the global scope without prior defined Java package.

umbrello/codeimport/import_utils.{h,cpp}
- Add function globalScope() returning the package of the global scope.

umbrello/codeimport/nativeimportbase.cpp
- In function parseFile() do not push a null pointer as the global
  scope; instead, push Import_Utils::globalScope().

CCBUG:368453