[ENH] simplify coercion in BaseDistribution._log_pdf and _pdf def…

…ault (#293)

Minor change that simplifies coercion in `BaseDistribution._log_pdf` and
`_pdf` default.

skpro/distributions/base/_base.py

@@ -545,8 +545,7 @@ def _pdf(self, x):
             )
             warn(self._method_error_msg("pdf", fill_in=approx_method))
 
-            if self.ndim > 0 and not isinstance(x, pd.DataFrame):
-                x = pd.DataFrame(x, index=self.index, columns=self.columns)
+            x = self._coerce_to_self_index_df(x, flatten=False)
             res = self.log_pdf(x=x)
             if isinstance(res, pd.DataFrame):
                 res = res.values
@@ -597,8 +596,7 @@ def _log_pdf(self, x):
             )
             warn(self._method_error_msg("log_pdf", fill_in=approx_method))
 
-            if self.ndim > 0 and not isinstance(x, pd.DataFrame):
-                x = pd.DataFrame(x, index=self.index, columns=self.columns)
+            x = self._coerce_to_self_index_df(x, flatten=False)
             res = self.pdf(x=x)
             if isinstance(res, pd.DataFrame):
                 res = res.values