Fix .btn-file class in less as well

less/buttons.less

@@ -82,17 +82,21 @@
     // input file btn 
     &.btn-file {
         position: relative;
-        width: 120px;
-        height: 35px;
         overflow: hidden;
         > input[type='file'] {
-            display: block !important;
-            width: 100% !important;
-            height: 35px !important;
-            opacity: 0 !important;
             position: absolute;
-            top: -10px;
-            cursor: pointer;
+            top: 0;
+            right: 0;
+            min-width: 100%;
+            min-height: 100%;
+            font-size: 100px;
+            text-align: right;
+            filter: alpha(opacity=0);
+            opacity: 0;
+            outline: none;
+            background: white;
+            cursor: inherit;
+            display: block;
         }
     }