Harden emote parsing (#3885)

tests/src/HighlightController.cpp

@@ -16,6 +16,8 @@
 using namespace chatterino;
 using ::testing::Exactly;
 
+namespace {
+
 class MockApplication : IApplication
 {
 public:
@@ -27,7 +29,7 @@ public:
     {
         return nullptr;
     }
-    Emotes *getEmotes() override
+    IEmotes *getEmotes() override
     {
         return nullptr;
     }
@@ -77,6 +79,8 @@ public:
     // TODO: Figure this out
 };
 
+}  // namespace
+
 class MockHelix : public IHelix
 {
 public: