apply just an optimization (#450)

frankenphp.c

@@ -594,8 +594,6 @@ void frankenphp_register_bulk_variables(char *known_variables[27],
     free(dynamic_variables[i]);
     free(dynamic_variables[i + 1]);
   }
-
-  free(dynamic_variables);
 }
 
 static void frankenphp_register_variables(zval *track_vars_array) {

frankenphp.go

@@ -546,8 +546,7 @@ func go_register_variables(rh C.uintptr_t, trackVarsArray *C.zval) {
 	fc := r.Context().Value(contextKey).(*FrankenPHPContext)
 
 	le := (len(fc.env) + len(r.Header)) * 2
-	dynamicVariablesArr := (**C.char)(C.malloc(C.size_t(le) * C.size_t(unsafe.Sizeof((*C.char)(nil)))))
-	dynamicVariables := unsafe.Slice(dynamicVariablesArr, le)
+	dynamicVariables := make([]*C.char, le)
 
 	var i int
 	// Add all HTTP headers to env variables
@@ -572,8 +571,13 @@ func go_register_variables(rh C.uintptr_t, trackVarsArray *C.zval) {
 		i++
 	}
 
+	var dynamicVariablesPtr **C.char = nil
+	if le > 0 {
+		dynamicVariablesPtr = &dynamicVariables[0]
+	}
+
 	knownVariables := computeKnownVariables(r)
-	C.frankenphp_register_bulk_variables(&knownVariables[0], dynamicVariablesArr, C.size_t(le), trackVarsArray)
+	C.frankenphp_register_bulk_variables(&knownVariables[0], dynamicVariablesPtr, C.size_t(le), trackVarsArray)
 
 	fc.env = nil
 }