Fix leaks on failure to obtain backend interface implementation

If wpe_load_object() fails to obtain the implementation for interfaces,
free the struct before the early error returns instead of leaking them.

Author: aperezdc

src/renderer-backend-egl.c

@@ -38,8 +38,10 @@ wpe_renderer_backend_egl_create(int host_fd)
         return 0;
 
     backend->interface = wpe_load_object("_wpe_renderer_backend_egl_interface");
-    if (!backend->interface)
+    if (!backend->interface) {
+        free(backend);
         return 0;
+    }
 
     backend->interface_data = backend->interface->create(host_fd);
 
@@ -77,8 +79,10 @@ wpe_renderer_backend_egl_target_create(int host_fd)
         return 0;
 
     target->interface = wpe_load_object("_wpe_renderer_backend_egl_target_interface");
-    if (!target->interface)
+    if (!target->interface) {
+        free(target);
         return 0;
+    }
 
     target->interface_data = target->interface->create(target, host_fd);
 
@@ -142,8 +146,10 @@ wpe_renderer_backend_egl_offscreen_target_create()
         return 0;
 
     target->interface = wpe_load_object("_wpe_renderer_backend_egl_offscreen_target_interface");
-    if (!target->interface)
+    if (!target->interface) {
+        free(target);
         return 0;
+    }
 
     target->interface_data = target->interface->create();