locale.c: Mv line of code later in fcn

This avoids setting this until needed.

locale.c

@@ -1605,7 +1605,6 @@ S_new_numeric(pTHX_ const char *newnum)
      *                  such platforms.
      */
 
-    PL_numeric_underlying = TRUE;
 
     /* Save the new name if it isn't the same as the previous one, if any */
     if (PL_numeric_name && strEQ(PL_numeric_name, newnum)) {
@@ -1616,6 +1615,10 @@ S_new_numeric(pTHX_ const char *newnum)
     PL_numeric_name = savepv(newnum);
     }
 
+    /* We are in the underlying locale until changed at the end of this
+     * function */
+    PL_numeric_underlying = TRUE;
+
 #  ifdef USE_POSIX_2008_LOCALE
 
     /* We keep a special object for easy switching to */