Replace transparent background of loading picture with black color

clappr version 0.4.1 do not support transparent background of loading image(poster.svg).
Loading image is showing twice.

public/poster.svg

@@ -123,9 +123,9 @@
      borderopacity="1.0"
      inkscape:pageopacity="0"
      inkscape:pageshadow="2"
-     inkscape:zoom="0.35355339"
-     inkscape:cx="245.20427"
-     inkscape:cy="476.48989"
+     inkscape:zoom="0.70710678"
+     inkscape:cx="598.94304"
+     inkscape:cy="369.64071"
      inkscape:document-units="px"
      inkscape:current-layer="layer2"
      inkscape:document-rotation="0"
@@ -145,7 +145,7 @@
         <dc:format>image/svg+xml</dc:format>
         <dc:type
            rdf:resource="http://purl.org/dc/dcmitype/StillImage" />
-        <dc:title></dc:title>
+        <dc:title />
       </cc:Work>
     </rdf:RDF>
   </metadata>
@@ -155,6 +155,13 @@
      inkscape:label="Ebene 2"
      style="display:inline"
      transform="translate(0,-87)">
+    <rect
+       style="fill:#000000;fill-opacity:1;stroke:none;stroke-width:0.26458332"
+       id="rect832"
+       width="297"
+       height="210"
+       x="0"
+       y="87" />
     <path
        id="path847"
        style="opacity:1;fill:#ffffff;fill-opacity:1;stroke:none;stroke-width:0.13872343px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1"