clang-format: Prevent assertion discovered by fuzzer.

llvm-svn: 236578
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 762f92c..31befad 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -1056,6 +1056,8 @@
 
   verifyNoCrash("/\\\n/");
   verifyNoCrash("/\\\n* */");
+  // The 0-character somehow makes the lexer return a proper comment.
+  verifyNoCrash(StringRef("/*\\\0\n/", 6));
 }
 
 TEST_F(FormatTest, KeepsParameterWithTrailingCommentsOnTheirOwnLine) {