enable x0/dx and y0/dx attributes for quiver

Author: emilykl

src/traces/quiver/defaults.js

@@ -11,13 +11,6 @@ module.exports = function supplyDefaults(traceIn, traceOut, defaultColor, layout
         return Lib.coerce(traceIn, traceOut, attributes, attr, dflt);
     }
 
-    // Quiver requires explicit x and y inputs (no x0/dx or y0/dy fallback).
-    // Check presence on traceIn and let handleXYDefaults validate lengths.
-    if(traceIn.x === undefined || traceIn.y === undefined) {
-        traceOut.visible = false;
-        return;
-    }
-
     var len = handleXYDefaults(traceIn, traceOut, layout, coerce);
     if(!len) {
         traceOut.visible = false;