diff --git a/geo.py b/geo.py
index bfba493..54c35da 100755
--- a/geo.py
+++ b/geo.py
@@ -743,11 +743,11 @@ class Model:
 
         #Encode data into the main block.
         #note: PackData should go first, otherwise other ptr types might point to the start of the data block, which would result in a 0 point, which is treated as not present.
-        self.pack_tris = self.geo.encodeMainDataPackedDeltas(self.tris, 3, len(self.tris), "I", 1)
-        self.pack_verts = self.geo.encodeMainDataPackedDeltas(self.verts, 3, len(self.verts), "f", 0x8000)
-        self.pack_norms = self.geo.encodeMainDataPackedDeltas(self.norms, 3, len(self.norms), "f", 0x100)
-        self.pack_sts = self.geo.encodeMainDataPackedDeltas(self.sts, 2, len(self.verts), "f", 0x1000)
-        self.pack_sts3 = self.geo.encodeMainDataPackedDeltas(self.sts3, 2, len(self.verts), "f", 0x8000)
+        self.pack_tris = self.geo.encodeMainDataPackedDeltas(self.tris, 3, self.tris and len(self.tris), "I", 1)
+        self.pack_verts = self.geo.encodeMainDataPackedDeltas(self.verts, 3, self.verts and len(self.verts), "f", 0x8000)
+        self.pack_norms = self.geo.encodeMainDataPackedDeltas(self.norms, 3, self.norms and len(self.norms), "f", 0x100)
+        self.pack_sts = self.geo.encodeMainDataPackedDeltas(self.sts, 2, self.sts and len(self.sts), "f", 0x1000)
+        self.pack_sts3 = self.geo.encodeMainDataPackedDeltas(self.sts3, 2, self.sts3 and len(self.sts3), "f", 0x8000)
         self.pack_weights = self.geo.encodeMainDataPacked(self.weights_data)
         self.pack_matidxs = self.geo.encodeMainDataPacked(self.matidxs_data)
         self.pack_grid = self.geo.encodeMainDataPacked(self.grid_data)
@@ -780,8 +780,8 @@ class Model:
         for t in self.tex_idx:
             texidx_data.encode("<HH", *t)
         self.tex_count = len(self.tex_idx)
-        self.vert_count = len(self.verts)
-        self.tri_count = len(self.tris)
+        self.vert_count = self.verts and len(self.verts) or 0
+        self.tri_count = self.tris and len(self.tris) or 0
         self.name_ptr = len(self.geo.header_objname_data)
         self.geo.header_objname_data += self.name + ZERO_BYTE
         self.geo.header_objnames.append(self.name)
@@ -1221,22 +1221,24 @@ class Geo:
         return self.models[-1]
 
 if __name__ == "__main__":
-    if len(sys.argv) <= 1:
+    if len(sys.argv) <= 1 or len(sys.argv) > 3:
         print("Usage:")
-        print("   %s <file_in> [<file_out>]")
+        print("   %s <file_in> [<file_out>]" % (sys.argv[0], ))
         print("Test loads a .geo file, dumps its content, and optionally writes its content out.")
         exit(0)
     fh = open(sys.argv[1], "rb")
+    geo = Geo()
+    geo.loadFromFile(fh)
+    fh.close()
     #print(sys.argv)
     if len(sys.argv) <= 2:
         fho = None
     else:
         fho = open(sys.argv[2], "wb")
-    geo = Geo()
-    geo.loadFromFile(fh)
     if fho is not None:
+        data = geo.saveToData()
         #geo.dump()
-        geo.saveToFile(fho)
+        fho.write(data)
     else:
         geo.dump()
     #print("%s" % [geo.header_data])