Reset the s:vim_pane when reattaching

Prior to this change, VTR could get confused and focus the wrong pane
after reattaching the runner pane.

Closes #38 - Detaching the runner pane does not reset the vim_pane

plugin/vim-tmux-runner.vim

@@ -185,6 +185,7 @@ function! s:BreakRunnerPaneToTempWindow()
     call s:SendTmuxCommand(full_command)
     let s:detached_window = s:LastWindowNumber()
     unlet s:runner_pane
+    unlet s:vim_pane
 endfunction
 
 function! s:RunnerDimensionSpec()
@@ -192,14 +193,6 @@ function! s:RunnerDimensionSpec()
     return dimensions
 endfunction
 
-function! s:_ReattachPane()
-    let join_cmd = join(["join-pane", "-s", ":".s:detached_window.".0",
-        \ s:RunnerDimensionSpec()])
-    call s:SendTmuxCommand(join_cmd)
-    unlet s:detached_window
-    let s:runner_pane = s:ActivePaneIndex()
-endfunction
-
 function! s:TmuxInfo(message)
   " TODO: this should accept optional target pane, default to current.
   " Pass that to TargetedCommand as "display-message", "-p '#{...}')
@@ -273,6 +266,7 @@ endfunction
 
 function! s:ReattachPane()
     if !s:DetachedPaneAvailable() | return | endif
+    let s:vim_pane = s:ActivePaneIndex()
     call s:_ReattachPane()
     call s:FocusVimPane()
     if g:VtrClearOnReattach
@@ -280,6 +274,14 @@ function! s:ReattachPane()
     endif
 endfunction
 
+function! s:_ReattachPane()
+    let join_cmd = join(["join-pane", "-s", ":".s:detached_window.".0",
+        \ s:RunnerDimensionSpec()])
+    call s:SendTmuxCommand(join_cmd)
+    unlet s:detached_window
+    let s:runner_pane = s:ActivePaneIndex()
+endfunction
+
 function! s:ReorientRunner()
     if !s:ValidRunnerPaneSet() | return | endif
     let temp_window = s:BreakRunnerPaneToTempWindow()