Fix _php_math_round UB

php_intlog10abs() is ill-defined for a zero value. Avoid calling it
altogether as there's nothing to round with a zero value.

Author: nikic

ext/standard/math.c

@@ -129,7 +129,7 @@ PHPAPI double _php_math_round(double value, int places, int mode) {
 	double tmp_value;
 	int precision_places;
 
-	if (!zend_finite(value)) {
+	if (!zend_finite(value) || value == 0.0) {
 		return value;
 	}