2 files changed, 19 insertions, 2 deletions
diff --git a/src/nvim/eval/executor.c b/src/nvim/eval/executor.c
index 26b7a627a6..5b92f217d1 100644
--- a/src/nvim/eval/executor.c
+++ b/src/nvim/eval/executor.c
@@ -31,7 +31,13 @@ static int tv_op_blob(typval_T *tv1, const typval_T *tv2, const char *op)
   }
 
   // Blob += Blob
-  if (tv1->vval.v_blob == NULL || tv2->vval.v_blob == NULL) {
+  if (tv2->vval.v_blob == NULL) {
+    return OK;
+  }
+
+  if (tv1->vval.v_blob == NULL) {
+    tv1->vval.v_blob = tv2->vval.v_blob;
+    tv1->vval.v_blob->bv_refcount++;
     return OK;
   }
 
diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 22e7f383a5..bd977523c6 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -3880,6 +3880,7 @@ static varnumber_T indexof_blob(blob_T *b, varnumber_T startidx, typval_T *expr)
     }
   }
 
+  const int called_emsg_start = called_emsg;
   for (varnumber_T idx = startidx; idx < tv_blob_len(b); idx++) {
     set_vim_var_nr(VV_KEY, idx);
     set_vim_var_nr(VV_VAL, tv_blob_get(b, (int)idx));
@@ -3887,6 +3888,10 @@ static varnumber_T indexof_blob(blob_T *b, varnumber_T startidx, typval_T *expr)
     if (indexof_eval_expr(expr)) {
       return idx;
     }
+
+    if (called_emsg != called_emsg_start) {
+      return -1;
+    }
   }
 
   return -1;
@@ -3916,6 +3921,7 @@ static varnumber_T indexof_list(list_T *l, varnumber_T startidx, typval_T *expr)
     }
   }
 
+  const int called_emsg_start = called_emsg;
   for (; item != NULL; item = TV_LIST_ITEM_NEXT(l, item), idx++) {
     set_vim_var_nr(VV_KEY, idx);
     tv_copy(TV_LIST_ITEM_TV(item), get_vim_var_tv(VV_VAL));
@@ -3926,6 +3932,10 @@ static varnumber_T indexof_list(list_T *l, varnumber_T startidx, typval_T *expr)
     if (found) {
       return idx;
     }
+
+    if (called_emsg != called_emsg_start) {
+      return -1;
+    }
   }
 
   return -1;
@@ -3942,7 +3952,8 @@ static void f_indexof(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     return;
   }
 
-  if ((argvars[1].v_type == VAR_STRING && argvars[1].vval.v_string == NULL)
+  if ((argvars[1].v_type == VAR_STRING
+       && (argvars[1].vval.v_string == NULL || *argvars[1].vval.v_string == NUL))
       || (argvars[1].v_type == VAR_FUNC && argvars[1].vval.v_partial == NULL)) {
     return;
   }