[fix](plsql) Fix plsql variable initialization (#33186)

fe/fe-core/src/main/antlr4/org/apache/doris/nereids/PLLexer.g4

@@ -208,7 +208,3 @@ SYSDATE: 'SYSDATE';
 VARIANCE: 'VARIANCE';
 
 DOT2: '..';
-
-LABEL_PL
-    : ([a-zA-Z] | DIGIT | '_')* ':'
-    ;

fe/fe-core/src/main/antlr4/org/apache/doris/nereids/PLParser.g4

@@ -522,7 +522,7 @@ for_range_stmt :        // FOR (Integer range) statement
      ;
 
 label_stmt :
-       LABEL_PL
+       IDENTIFIER COLON
      | LT LT IDENTIFIER GT GT
      ;
 

fe/fe-core/src/main/java/org/apache/doris/plsql/Exec.java

@@ -2085,12 +2085,6 @@ public class Exec extends org.apache.doris.nereids.PLParserBaseVisitor<Integer>
     public Integer visitLabel_stmt(Label_stmtContext ctx) {
         if (ctx.IDENTIFIER() != null) {
             exec.labels.push(ctx.IDENTIFIER().toString());
-        } else {
-            String label = ctx.LABEL_PL().getText();
-            if (label.endsWith(":")) {
-                label = label.substring(0, label.length() - 1);
-            }
-            exec.labels.push(label);
         }
         return 0;
     }

fe/fe-core/src/main/java/org/apache/doris/plsql/executor/DorisRowResult.java

@@ -59,7 +59,7 @@ public class DorisRowResult implements RowResult {
 
     @Override
     public boolean next() {
-        if (eof) {
+        if (eof || coord == null) {
             return false;
         }
         try {