fix(osx): only run Preview.app in man-preview if man page exists (#10222)

plugins/osx/osx.plugin.zsh

@@ -219,7 +219,8 @@ function quick-look() {
 }
 
 function man-preview() {
-  man -t "$@" | open -f -a Preview
+  # Don't let Preview.app steal focus if the man page doesn't exist
+  man -w "$@" &>/dev/null && man -t "$@" | open -f -a Preview || man "$@"
 }
 compdef _man man-preview