gh-40283: Fix segmentation fault in module element multiplication
    
Fixes #40282 . Explanation there.

performance measurement. Before:

```
sage: a = vector(ZZ, 10000)
sage: b = 2
sage: %timeit a*b
109 μs ± 3.03 μs per loop (mean ± std. dev. of 7 runs, 10,000 loops
each)
sage: %timeit a._lmul_(b)
110 μs ± 1.81 μs per loop (mean ± std. dev. of 7 runs, 10,000 loops
each)
```

after:

```
sage: sage: %timeit a*b
107 μs ± 527 ns per loop (mean ± std. dev. of 7 runs, 10,000 loops each)
sage: sage: %timeit a._lmul_(b)
107 μs ± 665 ns per loop (mean ± std. dev. of 7 runs, 10,000 loops each)
```

within measurement error.

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### ⌛ Dependencies

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URL: #40283
Reported by: user202729
Reviewer(s): Travis Scrimshaw

Author: Release Manager

src/sage/modules/free_module_element.pyx

@@ -4539,8 +4539,17 @@ cdef class FreeModuleElement_generic_dense(FreeModuleElement):
             sage: V = ZZ['x']^5
             sage: 5 * V.0
             (5, 0, 0, 0, 0)
+
+        TESTS:
+
+        Check :issue:`40282` is fixed::
+
+            sage: R.<x> = QQ[]
+            sage: M = span([[x, x^2+1], [1/x, x^3]], R)
+            sage: x * M.basis()[0]
+            (1, x^4)
         """
-        if left._parent is self._parent._base:
+        if left._parent is self._parent.coordinate_ring():
             v = [left._mul_(<RingElement>x) for x in self._entries]
         else:
             v = [left * x for x in self._entries]
@@ -4555,8 +4564,17 @@ cdef class FreeModuleElement_generic_dense(FreeModuleElement):
             (-2/3, 0, 2, 2/3*pi)
             sage: v * (2/3)                                                             # needs sage.symbolic
             (-2/3, 0, 2, 2/3*pi)
+
+        TESTS:
+
+        Check :issue:`40282` is fixed::
+
+            sage: R.<x> = QQ[]
+            sage: M = span([[x, x^2+1], [1/x, x^3]], R)
+            sage: M.basis()[0] * x
+            (1, x^4)
         """
-        if right._parent is self._parent._base:
+        if right._parent is self._parent.coordinate_ring():
             v = [(<RingElement>x)._mul_(right) for x in self._entries]
         else:
             v = [x * right for x in self._entries]