Natspec: Fix ICE when overriding a struct getter with a Natspec-documented return value and the name in the struct is different.

libsolidity/analysis/DocStringAnalyser.h

@@ -54,7 +54,8 @@ private:
 	void handleCallable(
 		CallableDeclaration const& _callable,
 		StructurallyDocumented const& _node,
-		StructurallyDocumentedAnnotation& _annotation
+		StructurallyDocumentedAnnotation& _annotation,
+		FunctionType const* _functionType = nullptr
 	);
 
 	langutil::ErrorReporter& m_errorReporter;