Fix inference for assignment of known object to reference

We cannot retain the ce information in that case, we have to
assume the ce may change indirectly through the reference.

Fixes oss-fuzz #46720.

Zend/tests/assign_obj_to_ref_inference.phpt

@@ -0,0 +1,21 @@
+--TEST--
+Assigning an object of known type to a reference variable
+--FILE--
+<?php
+
+class Test {
+    public int $x = 42;
+}
+
+function test() {
+    $r =& $o;
+    $o = new Test;
+    $r = new stdClass;
+    $r->x = 3.141;
+    var_dump(is_float($o->x));
+}
+test();
+
+?>
+--EXPECT--
+bool(true)

ext/opcache/Optimizer/zend_inference.c

@@ -2740,7 +2740,11 @@ static zend_always_inline int _zend_update_type_info(
 					tmp |= MAY_BE_DOUBLE;
 				}
 				UPDATE_SSA_TYPE(tmp, ssa_op->op1_def);
-				COPY_SSA_OBJ_TYPE(ssa_op->op2_use, ssa_op->op1_def);
+				if (tmp & MAY_BE_REF) {
+					UPDATE_SSA_OBJ_TYPE(NULL, 0, ssa_op->op1_def);
+				} else {
+					COPY_SSA_OBJ_TYPE(ssa_op->op2_use, ssa_op->op1_def);
+				}
 			}
 			if (ssa_op->result_def >= 0) {
 				if (tmp & MAY_BE_REF) {