Ensure widget is still mounted before showing popup

lib/src/screens/send/send_page.dart

@@ -339,7 +339,7 @@ class SendPage extends BasePage {
                         showErrorValidationAlert(context);
                         return;
                       }
-                      
+
                       await sendViewModel.createTransaction();
 
                     },
@@ -365,15 +365,17 @@ class SendPage extends BasePage {
     reaction((_) => sendViewModel.state, (ExecutionState state) {
       if (state is FailureState) {
         WidgetsBinding.instance.addPostFrameCallback((_) {
-          showPopUp<void>(
-              context: context,
-              builder: (BuildContext context) {
-                return AlertWithOneAction(
-                    alertTitle: S.of(context).error,
-                    alertContent: state.error,
-                    buttonText: S.of(context).ok,
-                    buttonAction: () => Navigator.of(context).pop());
-              });
+          if (context.mounted) {
+            showPopUp<void>(
+                context: context,
+                builder: (BuildContext context) {
+                  return AlertWithOneAction(
+                      alertTitle: S.of(context).error,
+                      alertContent: state.error,
+                      buttonText: S.of(context).ok,
+                      buttonAction: () => Navigator.of(context).pop());
+                });
+          }
         });
       }