[geary/wip/3.32-avatars: 46/50] Make TestCase.assert_string robust in the face of null actuals

[Michael Gratton <mjog src gnome org>]

commit 4e484e237dd9dab61d39617062d0209d7b93a8f5
Author: Michael Gratton <mike vee net>
Date:   Sat Mar 9 19:57:16 2019 +1100

    Make TestCase.assert_string robust in the face of null actuals

 test/test-case.vala | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)
---
diff --git a/test/test-case.vala b/test/test-case.vala
index bb684967..ef4228ec 100644
--- a/test/test-case.vala
+++ b/test/test-case.vala
@@ -53,11 +53,17 @@ public void assert_string(string expected, string? actual, string? context = nul
         if (a.length > 32) {
             a = a[0:32] + "…";
         }
-        string b = actual;
-        if (b.length > 32) {
-            b = b[0:32] + "…";
+        string? b = actual;
+        if (b != null) {
+            if (b.length > 32) {
+                b = b[0:32] + "…";
+            }
+        }
+        if (b != null) {
+            print_assert("Expected: \"%s\", was: \"%s\"".printf(a, b), context);
+        } else {
+            print_assert("Expected: \"%s\", was null".printf(a), context);
         }
-        print_assert("Expected: \"%s\", was: \"%s\"".printf(a, b), context);
         assert_not_reached();
     }
 }