[Issue 20946] Segfault by forward reference and undefined identifier

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20946

--- Comment #5 from uplink.coder at googlemail.com ---
fixed by c227dd4849acbac2f7ff741d1cf0736f23552d09
fix issue 20709 - Segmentation fault when importing nonexistent type

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