Fix error tests handling in reporting

[sofurihafe]

Description

This PR fixes error window popping up when not real but only error tests were generated as described in the issue.
The tests looks like the following:

public void testMethodWithException_errors() {
    // Couldn't generate some tests. List of errors:
    // 
    // 1 occurrences of:
    // Index 100 out of bounds for length 3
}

Now, in case of only error tests there is no error window.

Fixes # (1425)

Type of Change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Regression and integration tests

Automated Testing

utbot-samples.

Manual Scenario

Code from the issue did not cause the error window popping up, so it was decided to cause it artificially by tweaking CgTestClassConstructor.