Converted smart pointer for the rule context in RecognitionException

Since we pass around raw pointer for volatile references now, we must not create smart pointers from them or we will get a double free.

runtime/Cpp/runtime/src/RecognitionException.h

@@ -45,7 +45,7 @@ namespace antlr4 {
     /// The Recognizer where this exception originated.
     IRecognizer *_recognizer;
     IntStream *_input;
-    Ref<ParserRuleContext> _ctx;
+    ParserRuleContext *_ctx;
 
     /// The current Token when an error occurred. Since not all streams
     /// support accessing symbols by index, we have to track the Token
@@ -91,7 +91,7 @@ namespace antlr4 {
     /// </summary>
     /// <returns> The <seealso cref="RuleContext"/> at the time this exception was thrown.
     /// If the context is not available, this method returns {@code null}. </returns>
-    virtual Ref<RuleContext> getCtx() const;
+    virtual RuleContext* getCtx() const;
 
     /// <summary>
     /// Gets the input stream which is the symbol source for the recognizer where