Balloons not enabled in MacVim on startup

## Information

**VIM version**

VIM - Vi IMproved 8.1 (2018 May 17, compiled Jun 17 2018 23:04:26)
macOS version

Operating System: macOS 10.13.6

### :ALEInfo

Current Filetype: javascript
Available Linters: ['eslint', 'flow', 'jscs', 'jshint', 'standard', 'tsserver', 'xo']
Enabled Linters: ['eslint', 'flow']
Suggested Fixers:
'eslint' - Apply eslint --fix to a file.
'importjs' - automatic imports for javascript
'prettier' - Apply prettier to a file.
'prettier_eslint', 'prettier-eslint' - Apply prettier-eslint to a file.
'prettier_standard', 'prettier-standard' - Apply prettier-standard to a file.
'remove_trailing_lines' - Remove all blank lines at the end of a file.
'standard' - Fix JavaScript files using standard --fix
'trim_whitespace' - Remove all trailing whitespace characters at the end of every line.
'xo' - Fix JavaScript files using xo --fix.
Linter Variables:
let g:ale_javascript_eslint_executable = 'eslint'
let g:ale_javascript_eslint_options = ''
let g:ale_javascript_eslint_suppress_eslintignore = 0
let g:ale_javascript_eslint_suppress_missing_config = 0
let g:ale_javascript_eslint_use_global = 0
let g:ale_javascript_flow_executable = 'flow'
let g:ale_javascript_flow_use_global = 0
let g:ale_javascript_flow_use_home_config = 0
let g:ale_javascript_flow_use_respect_pragma = 1
Global Variables:
let g:ale_cache_executable_check_failures = v:null
let g:ale_change_sign_column_color = 0
let g:ale_command_wrapper = ''
let g:ale_completion_delay = v:null
let g:ale_completion_enabled = 0
let g:ale_completion_max_suggestions = v:null
let g:ale_echo_cursor = 1
let g:ale_echo_msg_error_str = 'Error'
let g:ale_echo_msg_format = '%code: %%s'
let g:ale_echo_msg_info_str = 'Info'
let g:ale_echo_msg_warning_str = 'Warning'
let g:ale_enabled = 1
let g:ale_fix_on_save = 1
let g:ale_fixers = {'javascript': ['remove_trailing_lines', 'trim_whitespace', 'importjs', 'prettier_eslint']}
let g:ale_history_enabled = 1
let g:ale_history_log_output = 1
let g:ale_keep_list_window_open = 0
let g:ale_lint_delay = 200
let g:ale_lint_on_enter = 1
let g:ale_lint_on_filetype_changed = 1
let g:ale_lint_on_save = 1
let g:ale_lint_on_text_changed = 'always'
let g:ale_lint_on_insert_leave = 0
let g:ale_linter_aliases = {}
let g:ale_linters = {'javascript': ['eslint', 'flow', 'flow-language-server']}
let g:ale_linters_explicit = 0
let g:ale_list_window_size = 10
let g:ale_list_vertical = 0
let g:ale_loclist_msg_format = '%code: %%s'
let g:ale_max_buffer_history_size = 20
let g:ale_max_signs = -1
let g:ale_maximum_file_size = v:null
let g:ale_open_list = 0
let g:ale_pattern_options = {}
let g:ale_pattern_options_enabled = 0
let g:ale_set_balloons = 1
let g:ale_set_highlights = 1
let g:ale_set_loclist = 1
let g:ale_set_quickfix = 0
let g:ale_set_signs = 1
let g:ale_sign_column_always = 0
let g:ale_sign_error = '>>'
let g:ale_sign_info = '--'
let g:ale_sign_offset = 1000000
let g:ale_sign_style_error = '>>'
let g:ale_sign_style_warning = '--'
let g:ale_sign_warning = '--'
let g:ale_statusline_format = v:null
let g:ale_type_map = {}
let g:ale_use_global_executables = v:null
let g:ale_warn_about_trailing_blank_lines = 1
let g:ale_warn_about_trailing_whitespace = 1
Command History:
(started) ['/bin/zsh', '-c', '''/Users/sdileep/Code/v1/node_modules/eslint/bin/eslint.js'' -f unix --stdin --stdin-filename ''/Users/sdileep/Code/v1/lib/rpc.js'
' < ''/var/folders/x7/87_48qfs5ps0lphhk284f8qw0000gn/T/vKtjEeP/21/rpc.js''']
(finished - exit code 1) ['/bin/zsh', '-c', '''/Users/sdileep/Code/v1/node_modules/eslint/bin/eslint.js'' -f unix --stdin --stdin-filename ''/Users/sdileep/Code
/v1/lib/rpc.js'' < ''/var/folders/x7/87_48qfs5ps0lphhk284f8qw0000gn/T/vKtjEeP/22/rpc.js''']
<<>>
/Users/sdileep/Code/v1/lib/rpc.js:79:10: Unnecessary 'else' after 'return'. [Error/no-else-return]
/Users/sdileep/Code/v1/lib/rpc.js:139:61: Unexpected block statement surrounding arrow body; parenthesize the returned value and move it immediately after the `
=>`. [Error/arrow-body-style]
/Users/sdileep/Code/v1/lib/rpc.js:146:61: Unexpected block statement surrounding arrow body; parenthesize the returned value and move it immediately after the `
=>`. [Error/arrow-body-style]
/Users/sdileep/Code/v1/lib/rpc.js:250:1: Line 250 exceeds the maximum line length of 100. [Error/max-len]
/Users/sdileep/Code/v1/lib/rpc.js:486:68: Unexpected use of comma operator. [Error/no-sequences]
/Users/sdileep/Code/v1/lib/rpc.js:567:64: Unexpected use of comma operator. [Error/no-sequences]
6 problems
<<>>
## What went wrong

Linter output, in this case from eslint, should show in a balloon on mouse hover but it does not unless I explicitly run :call ale#balloon#Enable() myself.

## Reproducing the bug

1. Open a JS file with some lint errors like missing semicolon, whitespace, etc with eslint set as one of your linters.
2. Hover the mouse over the error in the source or the >> symbols in the margin
3. No balloon tooltip with the error will appear
4. :call ale#balloon#Enable() and then hover again, and you will see the tooltips fine