eth_uninstallFilter should return false for non-existent filter (#8280)

* eth_uninstallFilter should return false for non-existent filter

* Use shorter form is_some()

rpc/src/v1/helpers/poll_manager.rs

@@ -74,8 +74,8 @@ impl<F, T> PollManager<F, T> where T: Timer {
 	}
 
 	/// Removes poll info.
-	pub fn remove_poll(&mut self, id: &PollId) {
-		self.polls.remove(id);
+	pub fn remove_poll(&mut self, id: &PollId) -> bool {
+		self.polls.remove(id).is_some()
 	}
 }
 

rpc/src/v1/impls/eth_filter.rs

@@ -242,7 +242,6 @@ impl<T: Filterable + Send + Sync + 'static> EthFilter for T {
 	}
 
 	fn uninstall_filter(&self, index: Index) -> Result<bool> {
-		self.polls().lock().remove_poll(&index.value());
-		Ok(true)
+		Ok(self.polls().lock().remove_poll(&index.value()))
 	}
 }