Handle null bool

Author: FabioBatSilva

php/ext/google/protobuf/convert.c

@@ -286,6 +286,9 @@ static bool to_double(zval* php_val, double* dbl) {
 
 static bool to_bool(zval* from, bool* to) {
   switch (Z_TYPE_P(from)) {
+    case IS_NULL:
+      *to = false;
+      return true;
     case IS_TRUE:
       *to = true;
       return true;

php/tests/optional_test.php

@@ -8,5 +8,7 @@
 $m = new TestMessage([]);
 
 $m->setTrueOptionalString(null);
+$m->setTrueOptionalBool(null);
 
 var_dump($m->getTrueOptionalString());
+var_dump($m->getTrueOptionalBool());