Merge pull request #12725 from acozzette/cherrypick-12104-fix

Fix crash in #12104 (cherry-pick)
diff --git a/src/google/protobuf/wire_format.h b/src/google/protobuf/wire_format.h
index dec6774..b1b42a9 100644
--- a/src/google/protobuf/wire_format.h
+++ b/src/google/protobuf/wire_format.h
@@ -357,8 +357,9 @@
 inline void WireFormat::VerifyUTF8String(const char* data, int size,
                                          WireFormat::Operation op) {
 #ifdef GOOGLE_PROTOBUF_UTF8_VALIDATION_ENABLED
-  WireFormatLite::VerifyUtf8String(
-      data, size, static_cast<WireFormatLite::Operation>(op), nullptr);
+  WireFormatLite::VerifyUtf8String(data, size,
+                                   static_cast<WireFormatLite::Operation>(op),
+                                   /* field_name = */ "");
 #else
   // Avoid the compiler warning about unused variables.
   (void)data;