Improve handling of invalid conversations

ts/state/ducks/conversations.ts

@@ -5459,6 +5459,16 @@ export function reducer(
     const { payload } = action;
     const { conversationId, messageId, switchToAssociatedView } = payload;
 
+    let conversation: ConversationType | undefined;
+
+    if (conversationId) {
+      conversation = getOwn(state.conversationLookup, conversationId);
+      if (!conversation) {
+        log.error(`Unknown conversation selected, id: [${conversationId}]`);
+        return state;
+      }
+    }
+
     const nextState = {
       ...omit(state, 'contactSpoofingReview'),
       selectedConversationId: conversationId,
@@ -5466,11 +5476,7 @@ export function reducer(
       targetedMessageSource: TargetedMessageSource.NavigateToMessage,
     };
 
-    if (switchToAssociatedView && conversationId) {
-      const conversation = getOwn(state.conversationLookup, conversationId);
-      if (!conversation) {
-        return nextState;
-      }
+    if (switchToAssociatedView && conversation) {
       return {
         ...omit(nextState, 'composer', 'selectedMessageIds'),
         showArchived: Boolean(conversation.isArchived),

ts/test-electron/state/ducks/conversations_test.ts

@@ -372,7 +372,7 @@ describe('both/state/ducks/conversations', () => {
     }
 
     describe('showConversation', () => {
-      it('selects a conversation id', () => {
+      it('does not select a conversation if it does not exist', () => {
         const state = {
           ...getEmptyState(),
         };
@@ -385,14 +385,44 @@ describe('both/state/ducks/conversations', () => {
         const action = dispatch.getCall(0).args[0];
         const nextState = reducer(state, action);
 
+        assert.isUndefined(nextState.selectedConversationId);
+        assert.isUndefined(nextState.targetedMessage);
+      });
+
+      it('selects a conversation id', () => {
+        const conversation = getDefaultConversation({
+          id: 'abc123',
+        });
+        const state = {
+          ...getEmptyState(),
+          conversationLookup: {
+            [conversation.id]: conversation,
+          },
+        };
+        const dispatch = sinon.spy();
+        showConversation({ conversationId: 'abc123' })(
+          dispatch,
+          getEmptyRootState,
+          null
+        );
+        const action = dispatch.getCall(0).args[0];
+        const nextState = reducer(state, action);
+
         assert.equal(nextState.selectedConversationId, 'abc123');
         assert.isUndefined(nextState.targetedMessage);
       });
 
       it('selects a conversation and a message', () => {
+        const conversation = getDefaultConversation({
+          id: 'abc123',
+        });
         const state = {
           ...getEmptyState(),
+          conversationLookup: {
+            [conversation.id]: conversation,
+          },
         };
+
         const dispatch = sinon.spy();
         showConversation({
           conversationId: 'abc123',