fix iwhere

Author: crusaderky

array_api_compat/common/_helpers.py

@@ -962,7 +962,12 @@ def iwhere(condition, x, y, /):
     x in place, if it's possible and beneficial for performance.    
     """
     if is_writeable_array(x):
-        x[condition] = y
+        if is_array_api_obj(y) and len(y.shape) > 0:
+            xp = array_namespace(x)
+            x, y = xp.broadcast_arrays(x, y)
+            x[condition] = y[condition]
+        else:
+            x[condition] = y
         return x
     else:
         xp = array_namespace(x)