Quote the variables in i3-sensible-* correctly

Previously, the variables $EDITOR, $PAGER, $TERMINAL and $VISUAL got
shell-expanded twice before executing them.

i3-sensible-editor

@@ -9,8 +9,8 @@
 # mechanism to find the preferred editor
 
 # Hopefully one of these is installed (no flamewars about preference please!):
-for editor in $VISUAL $EDITOR nano vim vi emacs pico qe mg jed gedit mc-edit; do
-    if command -v $editor > /dev/null 2>&1; then
-        exec $editor "$@"
+for editor in "$VISUAL" "$EDITOR" nano vim vi emacs pico qe mg jed gedit mc-edit; do
+    if command -v "$editor" > /dev/null 2>&1; then
+        exec "$editor" "$@"
     fi
 done