In android_set_abort_message, check for nullptr.

If a process is failing due to out of memory, some code calls
android_set_abort_message with a nullptr. Specifically, the libc++
library std::terminate can call do this. In this case, put a
null in the abort message.

Test: Call with nullptr and verify the code does not crash.
Test: Modified crasher to set an abort message and set a null abort
Test: message. Ran both, verified the abort message displays in
Test: first case, and doesn't display in the second case.
Change-Id: Ia9250f47e4537853ce93bbb20b35915a78caa502
diff --git a/tests/Android.bp b/tests/Android.bp
index 48149c7..2ea6087 100644
--- a/tests/Android.bp
+++ b/tests/Android.bp
@@ -343,6 +343,7 @@
         "__cxa_demangle_test.cpp",
         "alloca_test.cpp",
         "android_get_device_api_level.cpp",
+        "android_set_abort_message_test.cpp",
         "arpa_inet_test.cpp",
         "async_safe_test.cpp",
         "assert_test.cpp",