Fix gn typo

tools/gn/operators.cc

 // Copyright (c) 2013 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 "tools/gn/operators.h"
 
 #include <stddef.h>
 #include <algorithm>
 
 #include "base/strings/string_number_conversions.h"
@@ skipping 210 matching lines @@
   } else if (old_value.type() == Value::SCOPE) {
     type_name = "scope";
     empty_def = "{}";
   } else {
     NOTREACHED();
   }
 
   Err result(op_node->left()->GetRange(),
       "Replacing nonempty " + type_name + ".",
       "This overwrites a previously-defined nonempty " + type_name +
-      "with another nonempty " + type_name + ".");
+      " with another nonempty " + type_name + ".");
   result.AppendSubErr(Err(old_value, "for previous definition",
       "Did you mean to append/modify instead? If you really want to overwrite, "
       "do:\n"
       "  foo = " + empty_def + "\nbefore reassigning."));
   return result;
 }
 
 // -----------------------------------------------------------------------------
 
 Err MakeIncompatibleTypeError(const BinaryOpNode* op_node,
@@ skipping 532 matching lines @@
     return ExecuteGreaterEquals(scope, op_node, left_value, right_value, err);
   if (op.type() == Token::LESS_EQUAL)
     return ExecuteLessEquals(scope, op_node, left_value, right_value, err);
   if (op.type() == Token::GREATER_THAN)
     return ExecuteGreater(scope, op_node, left_value, right_value, err);
   if (op.type() == Token::LESS_THAN)
     return ExecuteLess(scope, op_node, left_value, right_value, err);
 
   return Value();
 }