RF: helper function for converting str to int

Add / use helper function for converting string to integer, where empty
string maps to 0.

Author: matthew-brett

nibabel/gifti/parse_gifti_fast.py

@@ -77,6 +77,11 @@ def read_data_block(encoding, endian, ordering, datatype, shape, data):
     return newarr
 
 
+def _str2int(in_str):
+    # Convert string to integer, where empty string gives 0
+    return int(in_str) if in_str else 0
+
+
 class GiftiImageParser(XmlParser):
 
     def __init__(self, encoding=None, buffer_size=35000000, verbose=0):
@@ -186,8 +191,8 @@ def StartElementHandler(self, name, attrs):
                 self.da.endian = gifti_endian_codes.code[attrs["Endian"]]
             if "ExternalFileName" in attrs:
                 self.da.ext_fname = attrs["ExternalFileName"]
-            if "ExternalFileOffset" in attrs and attrs["ExternalFileOffset"]:
-                self.da.ext_offset = int(attrs["ExternalFileOffset"])
+            if "ExternalFileOffset" in attrs:
+                self.da.ext_offset = _str2int(attrs["ExternalFileOffset"])
             self.img.darrays.append(self.da)
             self.fsm_state.append('DataArray')