fix #225: Help browser: Bad arguments for message 'open' to object 'pd'

pd/nw/dialog_search.html

@@ -300,12 +300,11 @@ function file_browser_click() {
 
 function file_browser_callback(elem) {
     var doc = elem.value;
-    //pdgui.post("file callback: file is " + elem.value);
-    //pdgui.post("dir is " + pdgui.defunkify_windows_path(path.dirname(doc)));
-    //pdgui.post("file is " + pdgui.defunkify_windows_path(path.basename(doc)));
-    pdgui.doc_open(pdgui.defunkify_windows_path(path.dirname(doc)),
-        pdgui.defunkify_windows_path(path.basename(doc)));
-    display_directory(pdgui.defunkify_windows_path(path.dirname(doc)));
+    if (doc !== "") {
+        pdgui.doc_open(pdgui.defunkify_windows_path(path.dirname(doc)),
+            pdgui.defunkify_windows_path(path.basename(doc)));
+        display_directory(pdgui.defunkify_windows_path(path.dirname(doc)));
+    }
 }
 
 function console_unwrap_tag(console_elem, tag_name) {