fix crash in inpaint when no seed in original image

Author: lstein

ldm/invoke/generator/inpaint.py

@@ -169,7 +169,8 @@ def get_make_image(self,prompt,sampler,steps,cfg_scale,ddim_eta,
             # Fill missing areas of original image
             init_filled = self.tile_fill_missing(
                 self.pil_image.copy(),
-                seed = self.seed if self.seed >= 0 else self.new_seed(),
+                seed = self.seed if (self.seed is not None
+                                     and self.seed >= 0) else self.new_seed(),
                 tile_size = tile_size
             )
             init_filled.paste(init_image, (0,0), init_image.split()[-1])