fixup outers via priorInvocation

This will fix the long standing issue with our scoped subs which are use-d by another
package with gets precompiled. This showed up for URI in rakudo star for example.

src/vm/jvm/runtime/org/perl6/nqp/sixmodel/SerializationReader.java

@@ -122,6 +122,7 @@ public void deserialize() {
         deserializeContexts();
         attachClosureOuters(crCount);
         attachContextOuters();
+        fixupContextOuters();
     }
 
     /* Checks the header looks sane and all of the places it points to make sense.
@@ -521,6 +522,15 @@ private void attachContextOuters() {
         }
     }
 
+    private void fixupContextOuters() {
+        for (int i = 0; i < contextTableEntries; i++) {
+            if (contexts[i].outer == null &&
+                contexts[i].codeRef.staticInfo.priorInvocation != null &&
+                contexts[i].codeRef.staticInfo.priorInvocation.outer != null)
+                contexts[i].outer = contexts[i].codeRef.staticInfo.priorInvocation.outer;
+        }
+    }
+
     public SixModelObject readRef() {
         short discrim = orig.getShort();
         int elems;