wasm: call "focus" on window, not canvas

This is necessary to have correct focus handling on webassembly/ubuntu
without this change tabbing from text input to f.ex a button would
not work.

Change-Id: I78eaa6202d8bdb87b1195d5c38a3f73570a49c90
Reviewed-by: Piotr Wierciński <piotr.wiercinski@qt.io>

src/plugins/platforms/wasm/qwasminputcontext.cpp

@@ -306,9 +306,10 @@ void QWasmInputContext::updateInputElement()
         m_inputElement["style"].set("height", "1px");
         m_inputElement.set("value", "");
 
-        m_inputElement.call<void>("blur");
         if (QWasmWindow *wasmwindow = QWasmWindow::fromWindow(focusWindow))
             wasmwindow->focus();
+        else
+            m_inputElement.call<void>("blur");
 
         return;
     }