revert: restore linebuffer.py LineOwnOperation.once() to avoid regression

Author: cloudQuant

backtrader/linebuffer.py

@@ -2427,12 +2427,46 @@ def once(self, start, end):
             start: Starting index.
             end: Ending index.
         """
+        # CRITICAL FIX: Ensure source operand is processed first
+        if self._parent_a is not None and hasattr(self._parent_a, "_once"):
+            try:
+                self._parent_a._once(start, end)
+            except Exception:
+                pass
+
+        # cache python dictionary lookups
         dst = self.array
         srca = self.a.array
         op = self.operation
 
+        # CRITICAL FIX: Ensure destination array is properly sized
+        while len(dst) < end:
+            dst.append(float("nan"))
+
+        # CRITICAL FIX: Ensure source array has required data
+        if len(srca) < end:
+            # If source array is shorter than required range, only process available data
+            end = min(end, len(srca))
+
         for i in range(start, end):
-            dst[i] = op(srca[i])
+            try:
+                # CRITICAL FIX: Bounds checking for source array
+                a_val = srca[i] if i < len(srca) else 0.0
+
+                # Ensure value is numeric
+                if a_val is None or (isinstance(a_val, float) and math.isnan(a_val)):
+                    a_val = 0.0
+
+                result = op(a_val)
+
+                # Ensure result is valid
+                if result is None or (isinstance(result, float) and math.isnan(result)):
+                    result = 0.0
+
+                dst[i] = result
+            except Exception:
+                # If operation fails, store 0.0
+                dst[i] = 0.0
 
     def size(self):
         """Return the number of lines in this LineActions object"""