Runtime support for invocables in ScriptGroups

This also includes support for InvokeID

Change-Id: I5b59df166ea30b309b8dd9623825ac0e72d03856
diff --git a/cpu_ref/rsCpuScript.cpp b/cpu_ref/rsCpuScript.cpp
index 3cec0b9..a618a17 100644
--- a/cpu_ref/rsCpuScript.cpp
+++ b/cpu_ref/rsCpuScript.cpp
@@ -898,6 +898,7 @@
     mCtx->unlockMutex();
     if (mScriptSO) {
         dlclose(mScriptSO);
+        mScriptSO = nullptr;
     }
     return false;
 }