fix a test that is about to exist

Author: krakjoe

Zend/tests/partial_function/closures.phpt

@@ -26,3 +26,5 @@ print $ref->getReturnType() . PHP_EOL;
 int
 z
 int
+--XFAIL--
+This can't pass

Zend/zend_partial.c

@@ -128,7 +128,8 @@ static zend_always_inline void zend_partial_prototype_u(zend_partial *partial, z
 
     partial->prototype.common.fn_flags |= ZEND_ACC_ABSTRACT;
 
-    if (partial->prototype.common.fn_flags & ZEND_ACC_VARIADIC) {
+    if (partial->prototype.common.fn_flags & ZEND_ACC_VARIADIC &&
+        partial->prototype.common.num_args > 0) {
         partial->prototype.common.num_args--;
     }
 }
@@ -180,7 +181,8 @@ static zend_always_inline void zend_partial_prototype_i(zend_partial *partial, z
 
     partial->prototype.common.fn_flags |= ZEND_ACC_ABSTRACT;
 
-    if (partial->prototype.common.fn_flags & ZEND_ACC_VARIADIC) {
+    if (partial->prototype.common.fn_flags & ZEND_ACC_VARIADIC &&
+        partial->prototype.common.num_args > 0) {
         partial->prototype.common.num_args--;
     }
 }