Fixed comma appended to username completion when not at the beginning of the message (#3060)

Co-authored-by: pajlada <rasmus.karlsson@pajlada.com>

tests/CMakeLists.txt

@@ -10,6 +10,7 @@ set(test_SOURCES
     ${CMAKE_CURRENT_LIST_DIR}/src/Emojis.cpp
     ${CMAKE_CURRENT_LIST_DIR}/src/ExponentialBackoff.cpp
     ${CMAKE_CURRENT_LIST_DIR}/src/TwitchAccount.cpp
+    ${CMAKE_CURRENT_LIST_DIR}/src/Helpers.cpp
     )
 
 add_executable(${PROJECT_NAME} ${test_SOURCES})