Fix a NULL-ptr deref

```
Program terminated with signal SIGSEGV, Segmentation fault.
20	  if (!(func->common.function_name)) {
(gdb) info locals
func = 0x0
function_name = 0xffb25f6d0190 "SearchByCallback"
complete_path_function = 0xffb26c8a0570 "\240\005\212l\262\377"
```

It seems that in some callback shenanigans, there is currently no non-NULL
`func` member in execute_data. PHP truly is marvelous.

This should close #515

1 files changed, 1 insertions, 1 deletions

diff --git a/src/sp_disabled_functions.c b/src/sp_disabled_functions.c
index 10a9466..050c023 100644
--- a/src/sp_disabled_functions.c
+++ b/src/sp_disabled_functions.c
@@ -17,7 +17,7 @@ char* get_complete_function_path(zend_execute_data const* const execute_data) {
     return NULL;  // LCOV_EXCL_LINE
   }
   const zend_function *const func = execute_data->func;
-  if (!(func->common.function_name)) {
+  if (!func || !(func->common.function_name)) {
     return NULL;
   }