Improve RS error handling.  On errors RS will now store the error and a message that can be read from the app.  RS will then not continue rendering frames while an unchecked error is present until new state is received.
diff --git a/libs/rs/rsScript.cpp b/libs/rs/rsScript.cpp
index cb1436b..a33933b 100644
--- a/libs/rs/rsScript.cpp
+++ b/libs/rs/rsScript.cpp
@@ -96,6 +96,10 @@
 void rsi_ScriptInvoke(Context *rsc, RsScript vs, uint32_t slot)
 {
     Script *s = static_cast<Script *>(vs);
+    if (s->mEnviroment.mInvokables[slot] == NULL) {
+        rsc->setError(RS_ERROR_BAD_SCRIPT, "Calling invoke on bad script");
+        return;
+    }
     s->setupScript();
     s->mEnviroment.mInvokables[slot]();
 }