remove background from group room list header button

res/img/icons-room-nobg.svg

@@ -0,0 +1,28 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<svg
+   xmlns:dc="http://purl.org/dc/elements/1.1/"
+   xmlns:cc="http://creativecommons.org/ns#"
+   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+   xmlns:svg="http://www.w3.org/2000/svg"
+   xmlns="http://www.w3.org/2000/svg"
+   xml:space="preserve"
+   style="enable-background:new 0 0 25 25;"
+   viewBox="0 0 25 25"
+   y="0px"
+   x="0px"
+   id="Layer_1"
+   version="1.1"><metadata
+   id="metadata11"><rdf:RDF><cc:Work
+       rdf:about=""><dc:format>image/svg+xml</dc:format><dc:type
+         rdf:resource="http://purl.org/dc/dcmitype/StillImage" /><dc:title></dc:title></cc:Work></rdf:RDF></metadata><defs
+   id="defs9">
+	
+	
+
+		
+	</defs>
+<path
+   style="fill:#9fa9ba;fill-opacity:1;stroke-width:1.24281836"
+   d="m 16.418416,10.445225 -0.763833,4.003888 h 3.564555 v 1.57729 h -3.819166 l -1.018445,5.095858 H 12.726556 L 13.745,16.026403 H 9.9258345 L 8.9073901,21.122261 H 7.2524182 L 8.2708625,16.026403 H 4.9609188 v -1.57729 H 8.5254735 L 9.416612,10.445225 H 5.9793629 V 8.989265 H 9.6712233 L 10.689667,3.7720766 h 1.782277 L 11.453501,8.989265 h 3.819166 L 16.29111,3.7720766 h 1.654972 L 16.927638,8.989265 h 3.309944 v 1.45596 h -3.819166 m -6.23797,4.125218 h 3.819166 l 0.763832,-4.003888 h -3.819166 l -0.763832,4.003888"
+   id="path3002" />
+</svg>

src/components/views/right_panel/GroupHeaderButtons.js

@@ -71,7 +71,7 @@ export default class GroupHeaderButtons extends HeaderButtons {
                 clickPhase={RightPanel.Phase.GroupMemberList}
                 analytics={['Right Panel', 'Group Member List Button', 'click']}
             />,
-            <HeaderButton key="_roomsButton" title={_t('Rooms')} iconSrc="img/icons-room.svg"
+            <HeaderButton key="_roomsButton" title={_t('Rooms')} iconSrc="img/icons-room-nobg.svg"
                 isHighlighted={isPhaseRoom}
                 clickPhase={RightPanel.Phase.GroupRoomList}
                 analytics={['Right Panel', 'Group Room List Button', 'click']}