Fix invalid YAML null value in logical_axis_rules for Wan and LTX2 configs

Author: Perseus14

src/maxdiffusion/configs/base_wan_14b.yml

@@ -174,7 +174,7 @@ logical_axis_rules: [
                       ['activation_batch', ['data', 'fsdp']],
                       ['activation_self_attn_heads', 'tensor'],
                       ['activation_cross_attn_q_length', 'tensor'],
-                      ['activation_length', None],
+                      ['activation_length', null],
                       ['activation_heads', 'tensor'],
                       ['mlp','tensor'],
                       ['embed', 'fsdp'],

src/maxdiffusion/configs/base_wan_1_3b.yml

@@ -147,7 +147,7 @@ logical_axis_rules: [
                       ['activation_batch', ['data', 'fsdp']],
                       ['activation_self_attn_heads', 'tensor'],
                       ['activation_cross_attn_q_length', 'tensor'],
-                      ['activation_length', None],
+                      ['activation_length', null],
                       ['activation_heads', 'tensor'],
                       ['mlp','tensor'],
                       ['embed', 'fsdp'],

src/maxdiffusion/configs/base_wan_27b.yml

@@ -158,7 +158,7 @@ logical_axis_rules: [
                       ['activation_batch', ['data', 'fsdp']],
                       ['activation_self_attn_heads', 'tensor'],
                       ['activation_cross_attn_q_length', 'tensor'],
-                      ['activation_length', None],
+                      ['activation_length', null],
                       ['activation_heads', 'tensor'],
                       ['mlp','tensor'],
                       ['embed', 'fsdp'],

src/maxdiffusion/configs/base_wan_i2v_14b.yml

@@ -153,7 +153,7 @@ logical_axis_rules: [
                       ['activation_batch', ['data', 'fsdp']],
                       ['activation_self_attn_heads', 'tensor'],
                       ['activation_cross_attn_q_length', 'tensor'],
-                      ['activation_length', None],
+                      ['activation_length', null],
                       ['activation_heads', 'tensor'],
                       ['mlp','tensor'],
                       ['embed', 'fsdp'],

src/maxdiffusion/configs/base_wan_i2v_27b.yml

@@ -154,7 +154,7 @@ logical_axis_rules: [
                       ['activation_batch', ['data', 'fsdp']],
                       ['activation_self_attn_heads', 'tensor'],
                       ['activation_cross_attn_q_length', 'tensor'],
-                      ['activation_length', None],
+                      ['activation_length', null],
                       ['activation_heads', 'tensor'],
                       ['mlp','tensor'],
                       ['embed', 'fsdp'],

src/maxdiffusion/configs/ltx2_video.yml

@@ -46,7 +46,7 @@ logical_axis_rules: [
                       ['activation_batch', ['data', 'fsdp']],
                       ['activation_self_attn_heads', 'tensor'],
                       ['activation_cross_attn_q_length', 'tensor'],
-                      ['activation_length', None],
+                      ['activation_length', null],
                       ['activation_heads', 'tensor'],
                       ['mlp','tensor'],
                       ['embed', 'fsdp'],