Don't overwrite any existing g:vdebug_features dictionary

Check to see whether it exists first before initializing it.

Author: joonty

plugin/vdebug.vim

@@ -58,6 +58,10 @@ if !exists("g:vdebug_keymap")
     let g:vdebug_keymap = {}
 endif
 
+if !exists("g:vdebug_features")
+    let g:vdebug_features = {}
+endif
+
 let g:vdebug_keymap_defaults = {
 \    "run" : "<F5>",
 \    "run_to_cursor" : "<F9>",
@@ -90,8 +94,6 @@ let g:vdebug_options_defaults = {
 \    "continuous_mode"  : 0
 \}
 
-let g:vdebug_features = {}
-
 " Different symbols for non unicode Vims
 if g:vdebug_force_ascii == 1
     let g:vdebug_options_defaults["marker_default"] = '*'