Fix random state regeneration logic in RandomState

Updated the _ensure_value_exists method to properly check the type of self._value and only regenerate the random state if it is not a numpy array, not a JAX Tracer, and has been deleted. This prevents unnecessary regeneration and ensures correct handling of different value types.

Author: Routhleck

brainpy/_src/math/random.py

@@ -546,12 +546,15 @@ def seed(self, seed_or_key=None, seed=None):
       key = seed_or_key
     self._value = key
 
+
   def _ensure_value_exists(self):
     """Ensure that the random state has a valid value, regenerate if needed."""
-    if not isinstance(self._value, np.ndarray) and self._value.is_deleted():
+    if not isinstance(self._value, np.ndarray):
       with jax.ensure_compile_time_eval():
-        seed_or_key = np.random.randint(0, 100000, 2, dtype=np.uint32)
-        self._value = seed_or_key
+        if not isinstance(self._value, jax.core.Tracer):
+          if self._value.is_deleted():
+            seed_or_key = np.random.randint(0, 100000, 2, dtype=np.uint32)
+            self._value = seed_or_key
 
 
   @property