patch 8.2.0378: prop_find() does not find all props

Problem:    prop_find() does not find all props.
Solution:   Check being in the start line. (Axel Forsman, closes #5776)
diff --git a/src/textprop.c b/src/textprop.c
index 4f5329e..6e3ed5f 100644
--- a/src/textprop.c
+++ b/src/textprop.c
@@ -663,13 +663,14 @@
 	    mch_memmove(&prop, text + textlen + i * sizeof(textprop_T),
 			    sizeof(textprop_T));
 
-	    if (dir < 0)
-	    {
-		if (col < prop.tp_col)
-		    break;
-	    }
-	    else if (prop.tp_col + prop.tp_len - (prop.tp_len != 0) < col)
-		continue;
+	    if (lnum == lnum_start)
+		if (dir < 0)
+		{
+		    if (col < prop.tp_col)
+			break;
+		}
+		else if (prop.tp_col + prop.tp_len - (prop.tp_len != 0) < col)
+		    continue;
 
 	    if (prop.tp_id == id || prop.tp_type == type_id)
 	    {