Remove a runtime comparison

There is no need to check every single time
if the corpus has been initialized: we can just add
the dummy `bytearray(0)` value at startup, and assume
that the corpus will never be empty.

pythonfuzz/corpus.py

@@ -409,6 +409,10 @@ def __init__(self, dirs=None, max_input_size=4096, mutators_filter=None, dict_pa
                     fname = os.path.join(path, i)
                     if os.path.isfile(fname):
                         self._add_file(fname)
+
+        if not self._inputs:
+            self.put(bytearray(0))
+
         self._seed_run_finished = not self._inputs
         self._seed_idx = 0
         self._save_corpus = dirs and os.path.isdir(dirs[0])
@@ -488,13 +492,8 @@ def generate_input(self):
                 self._seed_run_finished = True
             return next_input
 
-        if len(self._inputs) == 0:
-            zero_test_case = bytearray(0)
-            self.put(zero_test_case)
-            return zero_test_case
-        else:
-            buf = self._inputs[self._rand(len(self._inputs))]
-            return self.mutate(buf)
+        buf = self._inputs[self._rand(len(self._inputs))]
+        return self.mutate(buf)
 
     def mutate(self, buf):
         res = buf[:]