WIP another empty items fix

Author: JukkaL

mypyc/irbuild/vec.py

@@ -176,12 +176,13 @@ def vec_create_from_values(
     builder: LowLevelIRBuilder, vtype: RVec, values: list[Value], line: int
 ) -> Value:
     vec = vec_create(builder, vtype, len(values), line)
-    ptr = vec_items(builder, vec)
-    item_type = vtype.item_type
-    step = step_size(item_type)
-    for value in values:
-        builder.set_mem(ptr, item_type, value)
-        ptr = builder.int_add(ptr, step)
+    if values:
+        ptr = vec_items(builder, vec)
+        item_type = vtype.item_type
+        step = step_size(item_type)
+        for value in values:
+            builder.set_mem(ptr, item_type, value)
+            ptr = builder.int_add(ptr, step)
     builder.keep_alive([vec], line)
     return vec