[apps/shared] CurveView: avoid overflowing KDCoordinate

This fixes the following bug: add the sequence, u(n)=2^n. On the graph,
go to "sum of terms" and try to sum terms from 0 to 18 by moving the
cursor. It hangs.

apps/shared/curve_view.cpp

@@ -426,6 +426,10 @@ void CurveView::drawHorizontalOrVerticalSegment(KDContext * ctx, KDRect rect, Ax
     if (rect.intersects(lineRect)) {
       ctx->fillRect(lineRect, color);
     }
+    if (i > KDCOORDINATE_MAX - 2*dashSize) {
+      // Avoid overflowing KDCoordinate
+      break;
+    }
   }
 }