Fix crashes when a resolution method is passed to PrettyMethod.

Found by dump-oat-boot.

Change-Id: Icf670e37663c9761f64a683ea22a7a9c4df68b97
diff --git a/src/utils.cc b/src/utils.cc
index 389c280..a1c4b7a 100644
--- a/src/utils.cc
+++ b/src/utils.cc
@@ -273,6 +273,9 @@
   result += mh.GetName();
   if (with_signature) {
     std::string signature(mh.GetSignature());
+    if (signature == "<no signature>") {
+      return result + signature;
+    }
     result = PrettyReturnType(signature.c_str()) + " " + result + PrettyArguments(signature.c_str());
   }
   return result;
@@ -285,6 +288,9 @@
   result += dex_file.GetMethodName(method_id);
   if (with_signature) {
     std::string signature(dex_file.GetMethodSignature(method_id));
+    if (signature == "<no signature>") {
+      return result + signature;
+    }
     result = PrettyReturnType(signature.c_str()) + " " + result + PrettyArguments(signature.c_str());
   }
   return result;