Remove unnecessary convert_to_string_safe macro

I'm assuming that the reason this existed was to avoid modifying
an interned string. However, the current code handles this case
fine already.

ext/opcache/Optimizer/block_pass.c

@@ -81,13 +81,6 @@ int zend_optimizer_get_persistent_constant(zend_string *name, zval *result, int
 #define VAR_SOURCE(op) Tsource[VAR_NUM(op.var)]
 #define SET_VAR_SOURCE(opline) Tsource[VAR_NUM(opline->result.var)] = opline
 
-#define convert_to_string_safe(v) \
-	if (Z_TYPE_P((v)) == IS_NULL) { \
-		ZVAL_STRINGL((v), "", 0); \
-	} else { \
-		convert_to_string((v)); \
-	}
-
 static void strip_leading_nops(zend_op_array *op_array, zend_basic_block *b)
 {
 	zend_op *opcodes = op_array->opcodes;
@@ -311,10 +304,10 @@ static void zend_optimize_block(zend_basic_block *block, zend_op_array *op_array
 					int l, old_len;
 
 					if (Z_TYPE(ZEND_OP1_LITERAL(opline)) != IS_STRING) {
-						convert_to_string_safe(&ZEND_OP1_LITERAL(opline));
+						convert_to_string(&ZEND_OP1_LITERAL(opline));
 					}
 					if (Z_TYPE(ZEND_OP1_LITERAL(last_op)) != IS_STRING) {
-						convert_to_string_safe(&ZEND_OP1_LITERAL(last_op));
+						convert_to_string(&ZEND_OP1_LITERAL(last_op));
 					}
 					old_len = Z_STRLEN(ZEND_OP1_LITERAL(last_op));
 					l = old_len + Z_STRLEN(ZEND_OP1_LITERAL(opline));
@@ -694,10 +687,10 @@ static void zend_optimize_block(zend_basic_block *block, zend_op_array *op_array
 						int l, old_len;
 
 						if (Z_TYPE(ZEND_OP2_LITERAL(opline)) != IS_STRING) {
-							convert_to_string_safe(&ZEND_OP2_LITERAL(opline));
+							convert_to_string(&ZEND_OP2_LITERAL(opline));
 						}
 						if (Z_TYPE(ZEND_OP2_LITERAL(src)) != IS_STRING) {
-							convert_to_string_safe(&ZEND_OP2_LITERAL(src));
+							convert_to_string(&ZEND_OP2_LITERAL(src));
 						}
 
 						VAR_SOURCE(opline->op1) = NULL;