(core) Preventing empty string update on any column.

Summary: When editor is opened on any column and closed without entering any value, the column is converted to a text column.

Test Plan: browser tests

Reviewers: alexmojaki

Reviewed By: alexmojaki

Differential Revision: https://phab.getgrist.com/D3211

app/common/ValueParser.ts

@@ -32,6 +32,17 @@ export class ValueParser {
 
 }
 
+/**
+ * Same as basic Value parser, but will return null if a value is an empty string.
+ */
+class NullIfEmptyParser extends ValueParser {
+  public cleanParse(value: string): any {
+    if (value === "") {
+      return null;
+    }
+    return super.cleanParse(value);
+  }
+}
 
 export class NumericParser extends ValueParser {
   private _parse: NumberParse;
@@ -206,6 +217,7 @@ export class ReferenceListParser extends ReferenceParser {
 }
 
 export const valueParserClasses: { [type: string]: typeof ValueParser } = {
+  Any: NullIfEmptyParser,
   Numeric: NumericParser,
   Int: NumericParser,
   Date: DateParser,