Fix 0 char handling when encoding

The 0 char was encoded as just 0 (as the left->ch == 0 when it is a branch).
Fix is to first compare right index, and if it doesn't match then use last left.

tree.c

@@ -102,6 +102,7 @@ static int write_entry(struct BIT_BUFFER *bitbuf, struct tree *parent,
 		left = parent->left;
 		left = parent->left;
 		right = parent->right;
 		right = parent->right;
 
 
+		if (c != 0) {
 			if (left->ch == c) {
 			if (left->ch == c) {
 				int bit = 0;
 				int bit = 0;
 				bb_write(bitbuf, &bit, 1);
 				bb_write(bitbuf, &bit, 1);
@@ -111,6 +112,17 @@ static int write_entry(struct BIT_BUFFER *bitbuf, struct tree *parent,
 				bb_write(bitbuf, &bit, 1);
 				bb_write(bitbuf, &bit, 1);
 				break;
 				break;
 			}
 			}
+		} else {
+			if (left->left == NULL) {
+				int bit = 0;
+				bb_write(bitbuf, &bit, 1);
+				break;
+			} else if (right->ch == c) {
+				int bit = 1;
+				bb_write(bitbuf, &bit, 1);
+				break;
+			}
+		}
 
 
 		int bit = 0;
 		int bit = 0;
 		bb_write(bitbuf, &bit, 1);
 		bb_write(bitbuf, &bit, 1);