feat(inputcontainer): support showing inputcontainer without content

frontend/ui/widget/container/inputcontainer.lua

@@ -51,19 +51,21 @@ function InputContainer:_init()
 end
 
 function InputContainer:paintTo(bb, x, y)
+    if self[1] == nil then
+        return
+    end
+
     if not self.dimen then
         local content_size = self[1]:getSize()
         self.dimen = Geom:new{w = content_size.w, h = content_size.h}
     end
     self.dimen.x = x
     self.dimen.y = y
-    if self[1] then
-        if self.vertical_align == "center" then
-            local content_size = self[1]:getSize()
-            self[1]:paintTo(bb, x, y + math.floor((self.dimen.h - content_size.h)/2))
-        else
-            self[1]:paintTo(bb, x, y)
-        end
+    if self.vertical_align == "center" then
+        local content_size = self[1]:getSize()
+        self[1]:paintTo(bb, x, y + math.floor((self.dimen.h - content_size.h)/2))
+    else
+        self[1]:paintTo(bb, x, y)
     end
 end
 
@@ -97,6 +99,10 @@ function InputContainer:onGesture(ev)
 end
 
 function InputContainer:onInput(input)
+    if self.enter_callback == nil then
+        return
+    end
+
     local InputDialog = require("ui/widget/inputdialog")
     self.input_dialog = InputDialog:new{
         title = input.title or "",