R804 - fix crash caused by looking at a unique boulder symbol

The code only handled the case where the boulder symbol was non-unique.
Add code to handle the case where the boulder sym is the first match.

doc/fixes34.1

@@ -83,6 +83,7 @@ axes should chop trees; picks shouldn't
 chance to aim grappling hook when skilled or better
 level limit of monsters like naga hatchlings should be high enough to grow up
 scroll of enchant weapon will become discovered when read in some cases
+don't crash when using lookat on a boulder an BOULDER sym is unique
 
 
 Platform- and/or Interface-Specific Fixes

src/pager.c

@@ -656,8 +656,15 @@ do_look(quick)
 	}
 
 	/* handle optional boulder symbol as a special case */ 
-	if (iflags.bouldersym && sym == iflags.bouldersym)
+	if (iflags.bouldersym && sym == iflags.bouldersym) {
+	    if (!found) {
+		firstmatch = "boulder";
+		Sprintf(out_str, "%c       %s", sym, an(firstmatch));
+		found++;
+	    } else {
 		found += append_str(out_str, "boulder");
+	    }
+	}
 	
 	/*
 	 * If we are looking at the screen, follow multiple possibilities or