[shotwell] Fix a warning in JPEG sniffer

[Jens Georg <jensgeorg src gnome org>]

commit a0e56a0cb98c9f9bbb6c4f2d3185b7e12b4f6f07
Author: Jens Georg <mail jensge org>
Date:   Wed Oct 23 21:17:16 2019 +0200

    Fix a warning in JPEG sniffer

 src/photos/JfifSupport.vala | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/src/photos/JfifSupport.vala b/src/photos/JfifSupport.vala
index 17b38516..36450bd0 100644
--- a/src/photos/JfifSupport.vala
+++ b/src/photos/JfifSupport.vala
@@ -117,6 +117,7 @@ public class JfifSniffer : GdkSniffer {
     }
 
     private DetectedPhotoInformation? fast_sniff(out bool is_corrupted) throws Error {
+        is_corrupted = false;
         var detected = new DetectedPhotoInformation();
 
         detected.metadata = new PhotoMetadata();