Add buttons to prevent soft-lock in keybind conf.

libs/simple-button.lua

@@ -151,13 +151,13 @@ function button:press(x, y, touchID)
 end
 ---Trigger release action, don't need ``self._hovering`` to ``true``
 function button:release(x, y, touchID)
-    local valid = true
+    local valid
     if touchID then
         valid = touchID == self._touchID
     else
         valid = true
     end
-    
+
     if valid then
         self._pressed = false
         self._touchID = false
@@ -187,7 +187,7 @@ function BUTTON.checkDataValidation(D, safe)
         elseif type(D.text) ~= 'string' then
             error("[text] must be a string or a function returns string, got "..type(D.text))
         end
-    
+
         assert(type(D.x) == "number"            , "[x] must be a integer")
         assert(type(D.y) == "number"            , "[y] must be a integer")
         assert(type(D.w) == "number" and D.w > 0, "[w] must be a positive integer")