Fix #2690, don't cancel the shot process when the upload fails

Catch the particular request and connection errors that should not result in closing the selection, and do not tear down the selector in that case

addon/webextension/selector/shooter.js

@@ -69,6 +69,7 @@ this.shooter = (function() { // eslint-disable-line no-unused-vars
     // we use a timeout so in the case of a failure the button will
     // still start working again
     const uicontrol = global.uicontrol;
+    let deactivateAfterFinish = true;
     if (isSaving) {
       return;
     }
@@ -109,11 +110,21 @@ this.shooter = (function() { // eslint-disable-line no-unused-vars
       const copied = clipboard.copy(url);
       return callBackground("openShot", { url, copied });
     }, (error) => {
+      if ('popupMessage' in error && (error.popupMessage = "REQUEST_ERROR" || error.popupMessage == 'CONNECTION_ERROR')) {
+        // The error has been signaled to the user, but unlike other errors (or
+        // success) we should not abort the selection
+        deactivateAfterFinish = false;
+        return;
+      }
       if (error.name != "BackgroundError") {
         // BackgroundError errors are reported in the Background page
         throw error;
       }
-    }).then(() => uicontrol.deactivate()));
+    }).then(() => {
+      if (deactivateAfterFinish) {
+        uicontrol.deactivate();
+      }
+    }));
   };
 
   exports.downloadShot = function(selectedPos) {