Bug 1697836 - Avoid throwing when asking for a selection. r=emalysz

Selection may be null if the page got hidden in e.g., the afterprint
event listener or somewhere else.

Add a try catch for good measure, assuming there's no selection is
always safe.

I'll try to get an automated test-case for this working, though it might
be tricky.

Depends on D109714

Differential Revision: https://phabricator.services.mozilla.com/D109715

toolkit/actors/PrintingSelectionChild.jsm

@@ -22,9 +22,8 @@ class PrintingSelectionChild extends JSWindowActorChild {
     let focusedWindow = Services.focus.focusedWindow;
     if (focusedWindow) {
       let selection = focusedWindow.getSelection();
-      return selection.type == "Range";
+      return selection && selection.type == "Range";
     }
-
     return false;
   }
 }

toolkit/components/printing/content/printUtils.js

@@ -235,9 +235,11 @@ var PrintUtils = {
       let sourceActor = aBrowsingContext.currentWindowGlobal.getActor(
         "PrintingSelection"
       );
-      hasSelection = await sourceActor.sendQuery(
-        "PrintingSelection:HasSelection"
-      );
+      try {
+        hasSelection = await sourceActor.sendQuery(
+          "PrintingSelection:HasSelection"
+        );
+      } catch (ex) {}
     }
 
     let sourceBrowser = aBrowsingContext.top.embedderElement;