Fix attaching event listeners to all the clipboard buttons in the page

When the Clipboard object is created it attaches event listeners to the
given element or to all the elements that match the given DOM selector.
As all the clipboard buttons in the Talk UI (except the one in the empty
content view) have the "clipboard-button" CSS class all the Clipboard
objects listened to clicks on all the buttons, so clicking on a single
button triggered as many copies as buttons and thus Clipboard objects
were in the page. Now the Clipboard objects attach listeners only to
their corresponding clipboard button.

Note that it is not possible to use just one Clipboard object attached
to all the clipboard buttons, though, as the attached elements are fixed
when the Clipboard object is created and thus clipboard buttons added
after that are not taken into account. Therefore it is much easier to
keep track of a single button and create again its Clipboard object when
it is rerendered.

Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>

js/views/callinfoview.js

@@ -298,7 +298,11 @@
 		 * Clipboard
 		 */
 		initClipboard: function() {
-			var clipboard = new Clipboard('.clipboard-button');
+			if (this.ui.clipboardButton.length === 0) {
+				return;
+			}
+
+			var clipboard = new Clipboard(this.ui.clipboardButton[0]);
 			clipboard.on('success', function(e) {
 				var $input = $(e.trigger);
 				$input.tooltip('hide')

js/views/roomlistview.js

@@ -271,7 +271,11 @@
 		 * Clipboard
 		 */
 		initClipboard: function() {
-			var clipboard = new Clipboard('.clipboard-button');
+			if (this.ui.clipboardButton.length === 0) {
+				return;
+			}
+
+			var clipboard = new Clipboard(this.ui.clipboardButton[0]);
 			clipboard.on('success', function(e) {
 				var $input = $(e.trigger);
 				$input.tooltip('hide')