gn format: don't crash when there's no block on a function call

tools/gn/command_format.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <sstream>
 
 #include "base/command_line.h"
 #include "tools/gn/commands.h"
 #include "tools/gn/input_file.h"
 #include "tools/gn/parser.h"
@@ skipping 224 matching lines @@
         Sequence(kSequenceStyleBracedBlock,
                  condition->if_false()->AsBlock()->statements(),
                  condition->if_false()->AsBlock()->End());
       }
     }
   } else if (const FunctionCallNode* func_call = root->AsFunctionCall()) {
     Print(func_call->function().value());
     Sequence(kSequenceStyleFunctionCall,
              func_call->args()->contents(),
              func_call->args()->End());
-    Print(" ");
-    Sequence(kSequenceStyleBracedBlock,
-             func_call->block()->statements(),
-             func_call->block()->End());
+    if (func_call->block()) {
+      Print(" ");
+      Sequence(kSequenceStyleBracedBlock,
+               func_call->block()->statements(),
+               func_call->block()->End());
+    }
   } else if (const IdentifierNode* identifier = root->AsIdentifier()) {
     Print(identifier->value().value());
   } else if (const ListNode* list = root->AsList()) {
     Sequence(kSequenceStyleList, list->contents(), list->End());
   } else if (const LiteralNode* literal = root->AsLiteral()) {
     // TODO(scottmg): Quoting?
     Print(literal->value().value());
   } else if (const UnaryOpNode* unaryop = root->AsUnaryOp()) {
     Print(unaryop->op().value());
     Expr(unaryop->operand());
@@ skipping 140 matching lines @@
   }
   std::string output_string;
   if (FormatFileToString(input_name, dump_tree, &output_string)) {
     printf("%s", output_string.c_str());
   }
 
   return 0;
 }
 
 }  // namespace commands