function to find already existing keychains wasn't working properly

ChangeLog

@@ -1,5 +1,8 @@
  (Format: Year/Month/Day)
 Changes for 1.0rc3:
+*07/03/18:
+   * Fixed problem with new mouse binding code when using emacs keychains (Mark)
+     Keys.cc/hh
 *07/03/17:
    * Iconified, stuck windows weren't being moved to different workspaces (Mark)
      Screen.cc

src/Keys.hh

@@ -111,6 +111,8 @@ private:
 
         t_key *find(int type_, unsigned int mod_, unsigned int key_,
                     int context_) {
+            // t_key ctor sets context_ of 0 to GLOBAL, so we must here too
+            context_ = context_ ? context_ : GLOBAL;
             for (size_t i = 0; i < keylist.size(); i++) {
                 if (keylist[i]->type == type_ && keylist[i]->key == key_ &&
                     (keylist[i]->context & context_) > 0 && keylist[i]->mod ==