[shotwell/shotwell-0.24] Enable SQL debugging through environment variable

[Jens Georg <jensgeorg src gnome org>]

commit 10c3c72b8d7c73a96c38e36f24344789e539f0ed
Author: Jens Georg <mail jensge org>
Date:   Sun Oct 16 22:20:14 2016 +0200

    Enable SQL debugging through environment variable
    
    Signed-off-by: Jens Georg <mail jensge org>

 src/db/DatabaseTable.vala |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/db/DatabaseTable.vala b/src/db/DatabaseTable.vala
index 4fc8853..5ec5be1 100644
--- a/src/db/DatabaseTable.vala
+++ b/src/db/DatabaseTable.vala
@@ -53,7 +53,7 @@ public abstract class DatabaseTable {
         unowned string? sql_debug = Environment.get_variable
                                                          ("SHOTWELL_SQL_DEBUG");
 
-        if (sql_debug != "") {
+        if (sql_debug != null && sql_debug != "") {
             db.trace (on_trace);
         }
     }