Writing on an unidentified scroll of blank paper identifies paper

The character doesn't know that an unlabeled scroll is blank until
they look at the inside of the scroll, but that could be done
either by reading or by writing.

doc/fixes3-7-0.txt

@@ -1549,6 +1549,7 @@ you cannot sacrifice objects/corpses while stunned or confused
 'whatis' actions // and /? didn't work when the lootabc option was on, they
 	required /a and /c instead; add '/' and '?' as group accelerators so
 	that they work; /y and /n for them now only work when lootabc is off
+writing on an unidentified scroll of blank paper identifies blank paper
 
 
 Fixes to 3.7.0-x General Problems Exposed Via git Repository

src/write.c

@@ -105,7 +105,7 @@ dowrite(struct obj *pen)
                  : "scroll";
     if (Blind) {
         if (!paper->dknown) {
-            You("don't know if that %s is blank or not.", typeword);
+            You("don't know whether that %s is blank or not.", typeword);
             return ECMD_OK;
         } else if (paper->oclass == SPBOOK_CLASS) {
             /* can't write a magic book while blind */
@@ -120,6 +120,7 @@ dowrite(struct obj *pen)
         exercise(A_WIS, FALSE);
         return ECMD_TIME;
     }
+    makeknown(SCR_BLANK_PAPER);
 
     /* what to write */
     Sprintf(qbuf, "What type of %s do you want to write?", typeword);