Only start dragging on left mouse click

plugins/Sidebar/media/Sidebar.coffee

@@ -37,6 +37,8 @@ class Sidebar extends Class
 
 		# Detect dragging
 		@fixbutton.on "mousedown touchstart", (e) =>
+			if event.button > 0  # Right or middle click
+				return
 			e.preventDefault()
 
 			# Disable previous listeners

plugins/Sidebar/media/all.js

@@ -237,6 +237,9 @@ window.initScrollable = function () {
        */
       this.fixbutton.on("mousedown touchstart", (function(_this) {
         return function(e) {
+          if (event.button > 0) {
+            return;
+          }
           e.preventDefault();
           _this.fixbutton.off("click touchstop touchcancel");
           _this.fixbutton.off("mousemove touchmove");