Fixed crash on missing iso exif data

postprocess.c

@@ -307,8 +307,9 @@ read_exif(char *filename)
 
     if (TIFFGetField(im, EXIFTAG_PHOTOGRAPHICSENSITIVITY, &value_count, &short_array) != 1) {
         err("failed to read EXIFTAG_PHOTOGRAPHICSENSITIVITY");
+    }else {
+        imagedata.isospeed = short_array[0];
     }
-    imagedata.isospeed = short_array[0];
 
     if (TIFFGetField(im, EXIFTAG_FNUMBER, &imagedata.fnumber) != 1) {
         err("failed to read EXIFTAG_FNUMBER");