error on rendering a path

[scampi]

Error: Invalid value for <path> attribute d="M NaN,NaNL NaN,NaN"
    attrFunction @ d3.js:601
    (anonymous function) @ d3.js:884
    d3_selection_each @ d3.js:890
    d3_selectionPrototype.each @ d3.js:883
    d3_selectionPrototype.attr @ d3.js:583
    (anonymous function) @ eeg.js:1549
    event @ d3.js:437force.tick @ d3.js:6162
    d3_timer_mark @ d3.js:2076
    d3_timer_step @ d3.js:2056

The line in question is:

// depends on link.no property draw either straight line or curve
link.attr('d', function (d) {
    ...
})

[scampi]

this happens with the following graphs:

{
 "nodes": [
  {
   "id": "Companies",
   "label": "Companies",
   "nodeType": "company",
   "size": 30,
   "index": 0,
   "weight": 2,
   "x": 27.332126663066447,
   "y": 0,
   "px": 27.332126663066447,
   "py": 0
  },
  {
   "id": "Investments",
   "label": "Investments",
   "nodeType": "investment",
   "size": 30,
   "index": 1,
   "weight": 2,
   "x": 249.12898732256144,
   "y": 0,
   "px": 249.12898732256144,
   "py": 0
  },
  {
   "id": "Companies",
   "label": "Companies",
   "nodeType": "company",
   "size": 30,
   "index": 2,
   "weight": 0,
   "x": 293.2727792914957,
   "y": 0,
   "px": 293.2727792914957,
   "py": 0
  },
  {
   "id": "Articles",
   "label": "Articles",
   "nodeType": "article",
   "size": 30,
   "index": 3,
   "weight": 1,
   "x": 170.040128541179,
   "y": 0,
   "px": 170.040128541179,
   "py": 0
  },
  {
   "id": "Investor",
   "label": "Investor",
   "nodeType": "investor",
   "size": 30,
   "index": 4,
   "weight": 1,
   "x": 98.41379670845345,
   "y": 0,
   "px": 98.41379670845345,
   "py": 0
  },
  {
   "id": "Investments",
   "label": "Investments",
   "nodeType": "investment",
   "size": 30,
   "index": 5,
   "weight": 0,
   "x": 151.98775642784312,
   "y": 0,
   "px": 151.98775642784312,
   "py": 0
  }
 ],
 "links": [
  {
   "source": "Companies",
   "target": "Investments",
   "linkType": "link",
   "undirected": false,
   "htmlElement": {},
   "size": 1,
   "id": "Companies-Investments-link-0"
  },
  {
   "source": "Companies",
   "target": "Articles",
   "linkType": "link",
   "undirected": false,
   "htmlElement": {},
   "size": 1,
   "id": "Companies-Articles-link-0"
  },
  {
   "source": "Investor",
   "target": "Investments",
   "linkType": "link",
   "undirected": false,
   "htmlElement": {},
   "size": 1,
   "id": "Investor-Investments-link-0"
  }
 ]
}

and

{
 "nodes": [
  {
   "id": "article",
   "label": "article",
   "nodeType": "article",
   "size": 30,
   "index": 0,
   "weight": 1,
   "x": 331.8013362782076,
   "y": 0,
   "px": 331.8013362782076,
   "py": 0
  },
  {
   "id": "company",
   "label": "company",
   "nodeType": "company",
   "size": 30,
   "index": 1,
   "weight": 2,
   "x": 183.63235654402524,
   "y": 0,
   "px": 183.63235654402524,
   "py": 0
  },
  {
   "id": "company",
   "label": "company",
   "nodeType": "company",
   "size": 30,
   "index": 2,
   "weight": 0,
   "x": 68.99853831902146,
   "y": 0,
   "px": 68.99853831902146,
   "py": 0
  },
  {
   "id": "investment",
   "label": "investment",
   "nodeType": "investment",
   "size": 30,
   "index": 3,
   "weight": 2,
   "x": 344.6925353030674,
   "y": 0,
   "px": 344.6925353030674,
   "py": 0
  },
  {
   "id": "investment",
   "label": "investment",
   "nodeType": "investment",
   "size": 30,
   "index": 4,
   "weight": 0,
   "x": 212.41078704642132,
   "y": 0,
   "px": 212.41078704642132,
   "py": 0
  },
  {
   "id": "investor",
   "label": "investor",
   "nodeType": "investor",
   "size": 30,
   "index": 5,
   "weight": 1,
   "x": 195.8168082763441,
   "y": 0,
   "px": 195.8168082763441,
   "py": 0
  }
 ],
 "links": [
  {
   "source": "article",
   "target": "company",
   "linkType": "link",
   "undirected": false,
   "htmlElement": {},
   "size": 1,
   "id": "article-company-link-0"
  },
  {
   "source": "company",
   "target": "investment",
   "linkType": "link",
   "undirected": false,
   "htmlElement": {},
   "size": 1,
   "id": "company-investment-link-0"
  },
  {
   "source": "investment",
   "target": "investor",
   "linkType": "link",
   "undirected": false,
   "htmlElement": {},
   "size": 1,
   "id": "investment-investor-link-0"
  }
 ]
}