Follow-up fix for GH-13082

The font_obj should actually be NULL initialised, not the font gd
pointer.

Closes GH-13139.

Author: nielsdos

ext/gd/gd.c

@@ -2749,9 +2749,8 @@ static void php_imagechar(INTERNAL_FUNCTION_PARAMETERS, int mode)
 	gdImagePtr im;
 	int ch = 0, col, x, y, i, l = 0;
 	unsigned char *str = NULL;
-	zend_object *font_obj;
+	zend_object *font_obj = NULL;
 	zend_long font_int = 0;
-	gdFontPtr font = NULL;
 
 	ZEND_PARSE_PARAMETERS_START(6, 6)
 		Z_PARAM_OBJECT_OF_CLASS(IM, gd_image_ce)
@@ -2776,7 +2775,7 @@ static void php_imagechar(INTERNAL_FUNCTION_PARAMETERS, int mode)
 	y = Y;
 	x = X;
 
-	font = php_find_gd_font(font_obj, font_int);
+	gdFontPtr font = php_find_gd_font(font_obj, font_int);
 
 	switch (mode) {
 		case 0: