FieldRecord: Guard when field name is null

Field name relative offsets can be null if -strip-reflection-names
is passed to the frontend.

Author: bitjammer

include/swift/Reflection/Records.h

@@ -57,7 +57,9 @@ class FieldRecord {
   }
 
   std::string getFieldName()  const {
-    return FieldName.get();
+    if (FieldName)
+      return FieldName.get();
+    return "";
   }
 
   bool isObjC() const {

include/swift/Reflection/ReflectionContext.h

@@ -573,7 +573,10 @@ class ReflectionContext {
           if (!Unsubstituted)
             return {};
           auto Substituted = Unsubstituted->subst(*this, Subs);
-          Fields.push_back({Field.getFieldName(), Substituted});
+          auto FieldName = Field.getFieldName();
+          if (FieldName.empty())
+            FieldName = "<Redacted Field Name>";
+          Fields.push_back({FieldName, Substituted});
         }
       }
     }