fix crash with 23x23 (linux only); allow 6 blanks

Portuguese will want six blanks for a 21x21 board, so might as well
not crash in case that becomes a thing.

xwords4/common/dictnry.c

@@ -548,17 +548,23 @@ getCountsFor( const DictionaryCtxt* dict, XP_U16 nCols )
 
         /* don't have it in the wordlist? Extrapolate */
         if ( !found ) {
+            const Tile blank = dict_getBlankTile( dict );
+
             XP_U16 pct = (nCols * nCols * 100) / (15 * 15);
             XP_U8* src15 = dict->counts[15>>1];
             XP_ASSERT( !!src15 );
 
-            for ( int ii = 0; ii < dict->nFaces; ++ii ) {
-                XP_U16 count = src15[ii];
+            for ( Tile tile = 0; tile < dict->nFaces; ++tile ) {
+                XP_U16 count = src15[tile];
                 XP_U16 newCount = count * pct / 100;
                 if ( 50 < (count * pct) % 100 ) {
                     ++newCount;
                 }
-                counts[ii] = newCount;
+                XP_ASSERT( tile != blank || newCount <= MAX_NUM_BLANKS );
+                if ( tile == blank && newCount > MAX_NUM_BLANKS ) {
+                    newCount = MAX_NUM_BLANKS;
+                }
+                counts[tile] = newCount;
             }
         }
     }

xwords4/common/model.c

@@ -419,19 +419,24 @@ getSquareBonus( XP_U16 nCols, XP_U16 col, XP_U16 row )
         row = tmp;
     }
 
-    /* For a smaller board, skip the outer "rings" */
-    XP_U16 adj = (21 - nCols) / 2;
-    col += adj;
-    row += adj;
-
-    XP_U16 index = col;
-    for ( XP_U16 ii = 1; ii <= row; ++ii ) {
-        index += ii;
-    }
-
+    /* For a smaller board, skip the outer "rings." For larger,
+       outer rings are empty */
     XWBonusType result = BONUS_NONE;
-    if ( index < VSIZE(sTwentyOne)) {
-        result = sTwentyOne[index];
+    XP_U16 adj = (21 - nCols) / 2;
+    if ( 0 <= adj ) {
+        col += adj;
+        row += adj;
+
+        if ( col <= 21 && row <= 21 ) {
+            XP_U16 index = col;
+            for ( XP_U16 ii = 1; ii <= row; ++ii ) {
+                index += ii;
+            }
+
+            if ( index < VSIZE(sTwentyOne)) {
+                result = sTwentyOne[index];
+            }
+        }
     }
     return result;
 }

xwords4/common/model.h

@@ -51,8 +51,8 @@ extern "C" {
 #define CELL_OWNER(t) (((t)&CELL_OWNER_MASK) >> CELL_OWNER_OFFSET)
 
 #define MAX_UNIQUE_TILES 64 /* max tile non-blank faces */
-#define MAX_NUM_BLANKS 4
-
+/* Portuguese has 3 for a 15x15 game; can go higer on larger boards */
+#define MAX_NUM_BLANKS 6
 
 typedef struct BlankQueue {
     XP_U16 nBlanks;