[Enhancement] Add default avatar when profile image is not available (#188)

* Add default avatar when agent image is not available

* Remove fonts from avatar
Separate non-computed style values

yarn.lock

@@ -1234,6 +1234,14 @@
     source-map "~0.6.1"
     vue-template-es2015-compiler "^1.9.0"
 
+"@vue/test-utils@^1.0.0-beta.29":
+  version "1.0.0-beta.29"
+  resolved "https://registry.yarnpkg.com/@vue/test-utils/-/test-utils-1.0.0-beta.29.tgz#c942cf25e891cf081b6a03332b4ae1ef430726f0"
+  integrity sha512-yX4sxEIHh4M9yAbLA/ikpEnGKMNBCnoX98xE1RwxfhQVcn0MaXNSj1Qmac+ZydTj6VBSEVukchBogXBTwc+9iA==
+  dependencies:
+    dom-event-types "^1.0.0"
+    lodash "^4.17.4"
+
 "@webassemblyjs/ast@1.8.5":
   version "1.8.5"
   resolved "https://registry.yarnpkg.com/@webassemblyjs/ast/-/ast-1.8.5.tgz#51b1c5fe6576a34953bf4b253df9f0d490d9e359"
@@ -3352,6 +3360,11 @@ doctrine@^3.0.0:
   dependencies:
     esutils "^2.0.2"
 
+dom-event-types@^1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/dom-event-types/-/dom-event-types-1.0.0.tgz#5830a0a29e1bf837fe50a70cd80a597232813cae"
+  integrity sha512-2G2Vwi2zXTHBGqXHsJ4+ak/iP0N8Ar+G8a7LiD2oup5o4sQWytwqqrZu/O6hIMV0KMID2PL69OhpshLO0n7UJQ==
+
 dom-serializer@0:
   version "0.2.1"
   resolved "https://registry.yarnpkg.com/dom-serializer/-/dom-serializer-0.2.1.tgz#13650c850daffea35d8b626a4cfc4d3a17643fdb"