Fix regression in embed() from pull-request
#2096....
Fix regression in embed() from pull-request
#2096.
With certain sets of arguments `compile_flags` might be left as `None`. This
caused IPython to internally raise a TypeError when it tried to do a
bitwise or between `shell.compile.flags` and `PyCF_ONLY_AST` in
`CachingCompiler.ast_parse`.
The regression was introduced in:
b70ac12 embed(): Default to the future compile flags of the calling frame.
