Add an exception if a jpeg image is not a supported format

@@ -13,6 +13,7 @@
 - Fix Text decoration placements
 - Improve image buffer management
 - Optimize memory footprint
+- Add an exception if a jpeg image is not a supported format
 
 ## 1.5.0
 

@@ -64,6 +64,10 @@ class PdfJpegInfo {
       offset += len - 2;
     }
 
+    if (height == null) {
+      throw 'Unable to find a Jpeg image in the file';
+    }
+
     final Map<PdfExifTag, dynamic> tags = _findExifInJpeg(buffer);
 
     return PdfJpegInfo._(width, height, color, tags);