Added missing StandardConversionSequence initialization

This is the second msan failure where UserDefinedConversion does not initialize
its `Before` member as identity conversion.

llvm-svn: 199997
GitOrigin-RevId: df1a280526d7ad571c8cc69732bdf28e6b20d857
diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
index d5c13dd..2a3ab80 100644
--- a/lib/Sema/SemaOverload.cpp
+++ b/lib/Sema/SemaOverload.cpp
@@ -1134,6 +1134,7 @@
 
   if (UserDefResult == OR_Success) {
     ICS.setUserDefined();
+    ICS.UserDefined.Before.setAsIdentityConversion();
     // C++ [over.ics.user]p4:
     //   A conversion of an expression of class type to the same class
     //   type is given Exact Match rank, and a conversion of an