Don’t crash when conditionally defining classes with properties

src/Psalm/Internal/Analyzer/ClassAnalyzer.php

@@ -1541,9 +1541,7 @@ class ClassAnalyzer extends ClassLikeAnalyzer
             );
 
             if (!$declaring_property_class) {
-                throw new \UnexpectedValueException(
-                    'Cannot get declaring class for ' . $property_id
-                );
+                return;
             }
 
             $fq_class_name = $declaring_property_class;

tests/ClassTest.php

@@ -525,6 +525,14 @@ class ClassTest extends TestCase
                         echo A::SOME_CONST;
                     }'
             ],
+            'noCrashOnClassExists' => [
+                '<?php
+                    if (!class_exists(ReflectionGenerator::class)) {
+                        class ReflectionGenerator {
+                            private $prop;
+                        }
+                    }',
+            ]
         ];
     }