mRNA Fragments made by the Destroyer are grab-able and drag-able

[EthanWJohnson]

Seen on Windows 10 and MacOS

When a Destroyer is eating an mRNA segment, every one of the fragments it makes can be grabbed and dragged around the sim; it will not disappear until it is released.

Relevant Gif;

Relevant Issue: phetsims/tasks#776

Relevant debug info;
Name: ‪Gene Expression Essentials‬
URL: http://www.colorado.edu/physics/phet/dev/html/gene-expression-essentials/1.0.0-dev.2/gene-expression-essentials_en.html
Version: 1.0.0-dev.2 2017-01-30 19:21:44 UTC
Features missing: touch
User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36
Language: en-US
Window: 1680x930
Pixel Ratio: 1/1
WebGL: WebGL 1.0 (OpenGL ES 2.0 Chromium)
GLSL: WebGL GLSL ES 1.0 (OpenGL ES GLSL ES 1.0 Chromium)
Vendor: WebKit (WebKit WebGL)
Vertex: attribs: 16 varying: 30 uniform: 4096
Texture: size: 16384 imageUnits: 16 (vertex: 16, combined: 32)
Max viewport: 16384x16384
OES_texture_float: true
Dependencies JSON: {"assert":{"sha":"a707328c","branch":"master"},"axon":{"sha":"1cf10281","branch":"master"},"babel":{"sha":"10f77fec","branch":"master"},"brand":{"sha":"0be722ee","branch":"master"},"chipper":{"sha":"f4cd39bf","branch":"master"},"dot":{"sha":"75380061","branch":"master"},"gene-expression-essentials":{"sha":"9e5baa27","branch":"master"},"joist":{"sha":"d15e6fab","branch":"master"},"kite":{"sha":"6059ebb0","branch":"master"},"phet-core":{"sha":"84747dff","branch":"master"},"phetcommon":{"sha":"1cb33196","branch":"master"},"query-string-machine":{"sha":"d8a4ff18","branch":"master"},"scenery":{"sha":"550df01a","branch":"master"},"scenery-phet":{"sha":"b04d8086","branch":"master"},"sherpa":{"sha":"785a536c","branch":"master"},"sun":{"sha":"d0708aa5","branch":"master"},"tandem":{"sha":"d9c124e5","branch":"master"}}

[phet-steele]

Looks fixed, thanks @aadish.