Ensure sufficient available blocks remain if add_parfile fails (#2119)

* ensure sufficient available blocks remain if add_parfile fails

* replace while loop, drop use of pop()

sabnzbd/nzbstuff.py

@@ -1140,17 +1140,21 @@ def get_extra_blocks(self, setname: str, needed_blocks: int) -> int:
                     block_list.append(nzf)
                     avail_blocks += nzf.blocks
 
-        # Sort by smallest blocks last, to be popped first
-        block_list.sort(key=lambda x: x.blocks, reverse=True)
+        # Sort the smallest blocks first
+        block_list.sort(key=lambda x: x.blocks, reverse=False)
         logging.info("%s blocks available", avail_blocks)
 
         # Enough?
         if avail_blocks >= needed_blocks:
             added_blocks = 0
-            while added_blocks < needed_blocks:
-                new_nzf = block_list.pop()
+            for new_nzf in block_list:
                 if self.add_parfile(new_nzf):
                     added_blocks += new_nzf.blocks
+                    if added_blocks >= needed_blocks:
+                        break
+            else:
+                # End of block_list reached with insufficient blocks added
+                return 0
 
             logging.info("Added %s blocks to %s", added_blocks, self.final_name)
             return added_blocks