[Bugfix][multi_modal] Fix pos_ids being unitialized for minicpmv2.6 in hf runner (#51432)

Signed-off-by: Dino Music <Dino.Music@amd.com>

tests/models/multimodal/generation/vlm_utils/model_utils.py

@@ -922,6 +922,22 @@ def _internvl_generate(
     return outputs
 
 
+def _restore_resampler_pos_cache(hf_model: HfRunner) -> None:
+    """Recompute the resampler's 2D sin/cos position cache after loading.
+
+    `from_pretrained` materializes non-persistent buffers as uninitialized
+    memory, leaving `pos_embed` as zeros or NaN instead of the values computed
+    in `__init__`.
+    """
+    restored = 0
+    for module in hf_model.model.modules():
+        if not hasattr(module, "_set_2d_pos_cache"):
+            continue
+        module._set_2d_pos_cache(module.max_size, module.pos_embed.device)
+        restored += 1
+    assert restored, "no resampler pos cache found to restore"
+
+
 def minicpmv_25_patch_hf_runner(hf_model: HfRunner) -> HfRunner:
     orig_generate = hf_model.model.generate
 
@@ -965,6 +981,8 @@ def minicpmo_26_patch_hf_runner(hf_model: HfRunner) -> HfRunner:
 
 
 def minicpmv_26_patch_hf_runner(hf_model: HfRunner) -> HfRunner:
+    _restore_resampler_pos_cache(hf_model)
+
     orig_generate = hf_model.model.generate
 
     def _generate(self, *args, image_sizes=None, **kwargs):