autohide toolbox: clamp urlbar-input box block padding

When the user exits customize mode, Firefox re-evaluates urlbar
dimensions and the result ends up with --urlbar-height becoming 0px
since the urlbar gets hidden.

The input box uses --urlbar-height to calculate its block padding which
in turn evaluates to full urlbar-height - thus making the contents of
input-box 0px leading to "invisible" input-box.

As a workaround we now clamp the padding-block calculation to 4px.

chrome/autohide_toolbox.css

@@ -86,6 +86,11 @@ See the above repository for updates as well as full license text. */
 #navigator-toolbox[inFullscreen] > #PersonalToolbar,
 #PersonalToolbar[collapsed="true"]{ display: none }
 
+/* This is a bit hacky fix for an issue that will make urlbar zero pixels tall after you enter customize mode */
+#urlbar[breakout][breakout-extend] > .urlbar-input-container{
+  padding-block: calc(min(4px,(var(--urlbar-container-height) - var(--urlbar-height)) / 2) + var(--urlbar-container-padding)) !important;
+}
+
 /* Uncomment this if tabs toolbar is hidden with hide_tabs_toolbar.css */
  /*#titlebar{ margin-bottom: -9px }*/