reject non-printable characters from lokker entry

previously characters such as tab would be injected into the entry when pressed.
this is the same check which is used in various other places in efl for string
validation

src/modules/lokker/lokker.c

@@ -727,7 +727,7 @@ _lokker_cb_key_down(void *data EINA_UNUSED, int type EINA_UNUSED, void *event)
    else
      {
         /* here we have to grab a password */
-        if (ev->compose)
+        if (ev->compose && (ev->string[0] >= 0x20) && (ev->string[0] != 0x7f))
           {
              if (lokker_is_pin())
                {