From: zunda <zunda@freeshell.org>
Subject: Avoid returning random string value for an EXIF tag not present

* exif.c: Added a check whether the tag is found to rb_exif_get_tag().
  exif_entry_get_value() never returns NULL.
--- a/exif.c
+++ b/exif.c
@@ -214,7 +214,6 @@
 	Exif *exif;
 	ExifTag tag;
 	ExifEntry *e;
-	const char *found;
 	int i;
 	char value[1024];
 
@@ -250,8 +249,11 @@
 		if (e)
 			break;
 	}
-	found = exif_entry_get_value(e, value, sizeof(value));
-	return found ? rb_str_new2(found) : Qnil;
+	if (e){
+		exif_entry_get_value(e, value, sizeof(value));
+		return rb_str_new2(value);
+	}
+	return Qnil;
 }
 
 static void