Fix: Did not update caller frame object variable.

com.oracle.truffle.r.nodes/src/com/oracle/truffle/r/nodes/function/GetCallerFrameNode.java

@@ -61,6 +61,7 @@ public final class GetCallerFrameNode extends RBaseNode {
             if (slowPathFrame != null) {
                 return slowPathFrame;
             }
+            callerFrameObject = null;
         }
         assert callerFrameObject == null;