Merge pull request #1787 from marktucker/dev_udim_missing_first_tile

Fix UDIM file resolving when no "1001" file exists

(Internal change: 2218532)

pxr/usdImaging/usdImaging/materialParamUtils.cpp

@@ -121,7 +121,9 @@ _ResolvedPathForFirstTile(
         // naming pattern but the files that are linked do not. We'll
         // let whoever consumes the pattern determine if they want to
         // resolve symlinks themselves.
-        return resolver.Resolve(path);
+        path = resolver.Resolve(path);
+        if (!path.empty())
+            return path;
     }
     return std::string();
 }