[console] Fixed console print segfault on arrays (#1861)

The ZVAL_MUTABLE string was not initialized to a jerry_value_t
when the function returns, the auto-release mechanism will
will segfault.

Fixes #1858

Signed-off-by: Jimmy Huang <[email protected]>

Author: Jimmy Huang

src/zjs_console.c

@@ -54,11 +54,11 @@ static bool value2str(const jerry_value_t value, char *buf, int maxlen,
     //             is true
     //  returns: true if the representation was complete or false if it
     //             was abbreviated
-    ZVAL_MUTABLE str_val;
+    ZVAL_MUTABLE str_val = ZJS_UNDEFINED;
     bool is_string = false;
 
     if (jerry_value_is_array(value)) {
-        unsigned int len = jerry_get_array_length(value);
+        u32_t len = jerry_get_array_length(value);
         sprintf(buf, "[Array - length %u]", len);
         return false;
     } else if (jerry_value_is_boolean(value)) {