Do not stumble over forward declared struct member. 


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@62288 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/AsmPrinter/DwarfWriter.cpp b/lib/CodeGen/AsmPrinter/DwarfWriter.cpp
index f3ad9aa..4f115b1 100644
--- a/lib/CodeGen/AsmPrinter/DwarfWriter.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfWriter.cpp
@@ -1791,6 +1791,11 @@
       {
         // Add elements to structure type.
         DIArray Elements = CTy.getTypeArray();
+
+        // A forward struct declared type may not have elements available.
+        if (Elements.isNull())
+          break;
+
         // Add elements to structure type.
         for (unsigned i = 0, N = Elements.getNumElements(); i < N; ++i) {
           DIDescriptor Element = Elements.getElement(i);