protobuf: Fix a null/bool conversion.

third_party/protobuf/src/google/protobuf/io/coded_stream.cc

Index: third_party/protobuf/src/google/protobuf/io/coded_stream.cc
diff --git a/third_party/protobuf/src/google/protobuf/io/coded_stream.cc b/third_party/protobuf/src/google/protobuf/io/coded_stream.cc
index 57d486f958a274e86c0a1f2b843bfedc18611867..402a3ad36049f2c02ff809650d014265837ad3dc 100644
--- a/third_party/protobuf/src/google/protobuf/io/coded_stream.cc
+++ b/third_party/protobuf/src/google/protobuf/io/coded_stream.cc
@@ -452,7 +452,7 @@ bool CodedInputStream::ReadVarint64Fallback(uint64* value) {
 
     // We have overrun the maximum size of a varint (10 bytes).  The data
     // must be corrupt.
-    return NULL;
+    return false;
 
    done:
     Advance(ptr - buffer_);