Gvim: Empty bottom bar appears on re-sourcing vimrc - vim

Question

I recently decided to migrate to Gvim, and noticed that some of my gui-specific settings are borked.
I have defined an autocommand to re-source $MYVIMRC upon writing to it, and upon re-sourcing it (this does not happen on the initial startup), an empty bar appears on the bottom. I believe it is the bar that is meant to contain the horizontal scrollbar.
When I attempt to remove the scrollbar using
:set guioptions-=b
nothing happens. However, if I add it first and then remove it,
:set guioptions+=b
:set guioptions-=b
it disappears.
I thought this might be related to how and when I am defining my guioptions. This is the relevant part of my .vimrc:
set guioptions-=m " GUI: Disable Menu
set guioptions-=r " GUI: Disable right scrollbar
set guioptions-=T " GUI: Disable Toolbar
I attempted to put this in an augroup like this
augroup GuiWidgets
au!
set guioptions-=m " GUI: Disable Menu
set guioptions-=r " GUI: Disable right scrollbar
set guioptions-=T " GUI: Disable Toolbar
augroup end
but it made no difference.
What can be the source of this problem?
EDIT 1 - Added .vimrc
let mapleader = ','
inoremap jj <Esc>
set nocompatible
"********************************
" PLUGINS
"********************************
if has('vim_starting')
set runtimepath+=~/.vim/bundle/neobundle.vim/
endif
call neobundle#begin(expand('~/.vim/bundle/'))
NeoBundleFetch 'Shougo/neobundle.vim'
NeoBundle 'benmills/vimux'
NeoBundle 'scrooloose/nerdcommenter'
NeoBundle 'scrooloose/syntastic'
NeoBundle 'kana/vim-textobj-entire'
NeoBundle 'kana/vim-textobj-user'
NeoBundle 'Raimondi/delimitMate'
NeoBundle 'Lokaltog/vim-easymotion'
NeoBundle 'godlygeek/tabular'
NeoBundle 'surround.vim'
NeoBundle 'christoomey/vim-tmux-navigator'
NeoBundle 'Shougo/vimproc.vim'
NeoBundle 'Shougo/unite.vim'
NeoBundle 'Shougo/vimshell.vim'
NeoBundle 'c.vim'
call neobundle#end()
filetype plugin indent on
NeoBundleCheck
"******************************
" PLUGIN SETTINGS
"******************************
nnoremap <C-p> :Unite file_rec/async:! -silent -start-insert -auto-resize<CR>
"******************************
" PLUGIN MAPPINGS
"******************************
map <Space> <Plug>(easymotion-prefix)
cnoreabbrev bi Unite neobundle/install
cnoreabbrev bu Unite neobundle/update
cnoreabbrev bc NeoBundleClean
nmap <Leader>a= :Tabularize /=<CR>
vmap <Leader>a= :Tabularize /=<CR>
nmap <Leader>a: :Tabularize /:\zs<CR>
vmap <Leader>a: :Tabularize /:\zs<CR>
nmap <Leader>a# :Tabularize /#<CR>
vmap <Leader>a# :Tabularize /#<CR>
"******************************
" GENERAL SETTINGS
"******************************
set t_Co=256
let g:molokai_original=0
colorscheme molokai
filetype plugin indent on
syntax on
set complete-=t
set gfn=Source\ Code\ Pro\ 10
set encoding=utf-8
set number
set lazyredraw
set completeopt-=preview
set ttyfast
set backspace=indent,eol,start
set hidden
set showmatch
set wildmode=longest:list,full
set wildmenu
set shortmess+=I
set showcmd
set showmode
set clipboard=unnamed
set history=50
set nrformats=
set autoread
set ruler
set laststatus=2
set scrolloff=8
set visualbell
set splitright
set smarttab
set autoindent
set expandtab
set tabstop=4
set shiftwidth=4
set softtabstop=4
set ignorecase smartcase
set gdefault
set incsearch
set hlsearch
set nobackup
set noswapfile
set ttimeoutlen=50
set relativenumber
set cursorline
set cc=80
set guioptions-=m
set guioptions-=r
set guioptions-=T
"set guioptions=
match ErrorMsg '\%>80v.\+'
"***************************
" GENERAL MAPPINGS
"***************************
map cn <Esc>:cn<CR>
map cp <Esc>:cp<CR>
nmap <CR> o<Esc>k
inoremap {<CR> {<CR>}<C-o>O
nnoremap <leader>v :e $MYVIMRC<CR>
nnoremap <leader>h :let #/ = ""<CR>
nnoremap n nzz
nnoremap <silent> <leader>; :call setline('.', getline('.').';')<CR>
nnoremap <leader>q <C-w>q<CR>
nnoremap <leader>w :w<CR>
nnoremap <silent> <leader>d :bp\|bd #<CR>
nnoremap <leader>c :cd %:p:h<CR>
cnoreabbrev ci( %ci(
cnoreabbrev ci) %ci)
cnoreabbrev ci[ %ci[
cnoreabbrev ci[ %ci]
cnoreabbrev ci{ %ci{
cnoreabbrev ci} %ci}
"***************************
" AUTOCOMMANDS
"***************************
" Auto-source .vimrc
augroup Vimrc
au!
au bufwritepost .vimrc source $MYVIMRC
augroup end
" Filetype-specific settings
augroup Filetypes
au!
"au FileType c nmap <leader>r :SCCompileRun<CR>
au FileType c nmap <leader>r :make\|!./%:r<CR>
au FileType c setlocal sw=2 sts=2
au FileType ruby nmap <leader>r :call RunByFiletype("ruby")<CR>
augroup end
EDIT 2 - Added pictures (sorry for the small size)
On startup
After sourcing .vimrc (the empty scrollbar container appears)
After running :set guioptions+=b (the horizontal scrolling bar is added to the container)
After running :set guioptions-=b (the horizontal container disappears)
After running :set gfn=Source\ Code\ Pro\ 10 (the bar reappears)

Answer 1

Here is Vim in a terminal
Another example where I've tiled GVim to the upper right corner
The normal edge size is on the left, while on the right, is a forced edge size due to tiling and font height.

Answer 2

Ended up creating a block to initialize the GUI-specific options I wanted to set at startup and to not be subject of resourcing of .vimrc. I will no longer see the "instant effect" of changing the guifont in $MYVIMRC, but this will keep the bottom-bar from appearing.
if has('gui_running')
if has('vim_starting')
set gfn=Source\ Code\ Pro\ 10
set guioptions-=m
set guioptions-=T
set guioptions-=r
set guioptions+=c
endif
endif