Nest JBIG2 prediction if statements together

ltp can only become truthy if predition is true.

src/core/jbig2.js

@@ -269,11 +269,11 @@ var Jbig2Image = (function Jbig2ImageClosure() {
       if (prediction) {
         var sltp = decoder.readBit(contexts, pseudoPixelContext);
         ltp ^= sltp;
-      }
         if (ltp) {
-        bitmap.push(bitmap[bitmap.length - 1]); // duplicate previous row
+          bitmap[i] = row;//bitmap[i - 1]); // duplicate previous row
           continue;
         }
+      }
       var row = new Uint8Array(width);
       bitmap.push(row);
       for (j = 0; j < width; j++) {