If a set of runcodes starts with runcode 32 through 34, jbig2dec throws an
"error decoding symbol id table: run length with no antecedent!" because no
previous runcode was defined, from which to copy the PREFIXLEN.  

However, this check should only apply to runcode 32, since 33 and 34 use a
PREFIXLEN of zero.

Patch:


Index: jbig2_text.c
===================================================================
--- jbig2_text.c	(revision 464)
+++ jbig2_text.c	(working copy)
@@ -141,13 +141,13 @@
 	    len = code;
 	    range = 1;
 	  } else {
-	    if (index < 1) {
-	      jbig2_error(ctx, JBIG2_SEVERITY_FATAL, segment->number,
-		"error decoding symbol id table: run length with no antecedent!");
-	      /* todo: memory cleanup */
-	      return -1;
-	    }
 	    if (code == 32) {
+    	    if (index < 1) {
+    	      jbig2_error(ctx, JBIG2_SEVERITY_FATAL, segment->number,
+    		"error decoding symbol id table: run length with no antecedent!");
+    	      /* todo: memory cleanup */
+    	      return -1;
+    	    }
 	      len = symcodelengths[index-1].PREFLEN;
 	    } else {
 	      len = 0; /* code == 33 or 34 */