Don’t do new isset conversion on try-set vars

src/Psalm/Internal/Analyzer/Statements/Expression/AssertionFinder.php

@@ -491,6 +491,7 @@ class AssertionFinder
                         && ($var_type = $source->node_data->getType($isset_var))
                         && !$var_type->isMixed()
                         && !$var_type->possibly_undefined
+                        && !$var_type->possibly_undefined_from_try
                         && $var_name !== '$_SESSION'
                     ) {
                         $if_types[$var_name] = [['!null']];

tests/TryCatchTest.php

@@ -465,6 +465,16 @@ class TryCatchTest extends TestCase
                 [],
                 '8.0'
             ],
+            'issetInCatch' => [
+                '<?php
+                    function foo() : void {
+                        try {
+                            $a = 0;
+                        } catch (Exception $e) {
+                            echo isset($a) ? $a : 1;
+                        }
+                    }'
+            ],
         ];
     }