Remove a Redundant Conditional Check

The existing code check for `where_bounds.is_empty()` twice when
it can be combined into one. Moreover, the refactored code reads
better and feels straightforward.

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -959,11 +959,10 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                      \n    where\n        T: {qself_str},\n{}",
                     where_bounds.join(",\n"),
                 ));
-            }
-            let reported = err.emit();
-            if !where_bounds.is_empty() {
+                let reported = err.emit();
                 return Err(reported);
             }
+            err.emit();
         }
 
         Ok(bound)