fix: prevent fatal error when using emulator without grpc (#7588)

.github/emulator/start-emulator.sh

@@ -18,3 +18,4 @@ CONTAINER=`docker run \
   $IMAGE gcloud beta emulators $1 start --host-port=0.0.0.0:8085 --project=emulator-project`
 sleep 10
 docker logs $CONTAINER
+

Core/src/EmulatorTrait.php

@@ -36,17 +36,21 @@ private function emulatorGapicConfig($emulatorHost)
             $emulatorHost = str_replace($search, '', $emulatorHost);
         }
 
-        return [
+        $config = [
             'apiEndpoint' => $emulatorHost,
-            'transportConfig' => [
+            'credentials' => new InsecureCredentialsWrapper(),
+        ];
+        if (class_exists('Grpc\ChannelCredentials')) {
+            $config['transportConfig'] = [
                 'grpc' => [
                     'stubOpts' => [
                         'credentials' => \Grpc\ChannelCredentials::createInsecure()
                     ]
                 ]
-            ],
-            'credentials' => new InsecureCredentialsWrapper(),
-        ];
+            ];
+        }
+
+        return $config;
     }
     /**
      * Retrieve a valid base uri for a service emulator.

Core/tests/Unit/EmulatorTraitTest.php

@@ -50,6 +50,23 @@ public function testEmulatorGapicConfig($hostname, $expected = null)
         $this->assertNull($res['transportConfig']['grpc']['stubOpts']['credentials']);
     }
 
+
+    /**
+     * @dataProvider hostnames
+     */
+    public function testEmulatorGapicConfigWithNoGrpc($hostname, $expected = null)
+    {
+        if (\extension_loaded('grpc')) {
+            $this->markTestSkipped("Cannot run test with grpc extension loaded");
+        }
+
+        $expected = $expected ?: $hostname;
+
+        $res = $this->impl->call('emulatorGapicConfig', [$hostname]);
+        $this->assertEquals($expected, $res['apiEndpoint']);
+        $this->assertArrayNotHasKey('transportConfig', $res);
+    }
+
     public function hostnames()
     {
         return [